Your post is not a thing, and it has no concept of a single “owner” who could decide anything and everything concerning the post. In reality, there are multiple rights associated with the post that are held by multiple parties:

• You hold the copyright to the post content. This means that others cannot distribute the post or derived works without your permission. You are free to publish the post or its modified versions anywhere else you see fit (as long as you either own the means of publication, or their owner agrees with it, of course).

• Stack Exchange holds broad rights to distribute and otherwise use the post and its derived versions. You (the copyright holder) gave them these rights under the Terms of Service that you agreed with by posting the content here. You also agreed to give everybody similar distribution rights under the terms of the CC-BY-SA licence.

• MathOverflow the company owns the mathoverflow.net domain and rights to the MathOverflow name. They give Stack Exchange the right to use them under certain terms.

• Stack Exchange owns the servers that run the site. This gives them the right to decide what content to publish on the website, subject to legal and contractual obligations (including the above-mentioned user content licences and the agreement between Stack Exchange and MathOverflow). They delegate this right to users and moderators of the site under the various rules established on the site. Thus, in particular:

  If the author of a question on MathOverflow owns that question, then the author should be able to edit his/her own question in any way that he/she wants, including removing it completely and replacing it (literally) with the word Hello, for example.

  No, the author cannot do that, unless authorized so by Stack Exchange. That is, the author, being the copyright holder, can edit the question in any way they want and publish it on their own website, but they cannot post it here unless they conform to the rules of this site.

Your post is not a tangible thing, and bears no concept of a single “owner” who could decide anything and everything concerning the post. Rather, there are multiple rights associated with the post that are held by multiple parties:

• You hold the copyright to the post content. This means that others cannot distribute the post or derived works without your permission (but see the next point). You are free to publish the post or its modified versions anywhere else you see fit (as long as you either own the means of publication, or their owner agrees with it, of course).

• Stack Exchange holds broad rights to distribute and otherwise use the post and its derived versions. You (the copyright holder) gave them these rights under the Terms of Service that you agreed with by posting the content here. You also agreed to give everybody similar distribution rights under the terms of the CC-BY-SA licence.

• MathOverflow the corporation owns the mathoverflow.net domain and rights to the MathOverflow name. They give Stack Exchange the right to use them under certain terms.

• Stack Exchange owns the servers that run the site. This gives them the right to decide what content to publish on the website, subject to legal and contractual obligations (including the above-mentioned user content licences and the agreement between Stack Exchange and MathOverflow). They delegate this right to users and moderators of the site under the various rules established on the site. Thus, in particular:

  If the author of a question on MathOverflow owns that question, then the author should be able to edit his/her own question in any way that he/she wants, including removing it completely and replacing it (literally) with the word Hello, for example.

  No, the author cannot do that, unless authorized so by Stack Exchange. That is, the author, being the copyright holder, can edit the question in any way they want and publish it on their own website, but they cannot post it here unless they conform to the rules of this site.

Your post is not a thing, and it has no concept of a single “owner” who could decide anything and everything concerning the post. In reality, there are multiple rights associated with the post that are held by multiple parties:

• You hold the copyright to the post contents. This means that others cannot distribute the post or derived works without your permission. You are free to publish the post or its modified versions anywhere else you see fit (as long as you either own the means of publication, or their owner agrees with it, of course).

• Stack Exchange holds broad rights to distribute and otherwise use the post and its derived versions. You (the copyright holder) gave them these rights under the Terms of Service that you agreed with by posting the content here. You also agreed to give everybody similar distribution rights under the terms of the CC-BY-SA licence.

• MathOverflow the company owns the mathoverflow.net domain and rights to the MathOverflow name. They give Stack Exchange the right to use them under certain terms.

• Stack Exchange owns the servers that run the site. This gives them the right to decide what content to publish on the website, subject to legal and contractual obligations (including the above-mentioned user content licences and the agreement between Stack Exchange and MathOverflow). They delegate this right to users and moderators of the site under the various rules established on the site. Thus, in particular:

  If the author of a question on MathOverflow owns that question, then the author should be able to edit his/her own question in any way that he/she wants, including removing it completely and replacing it (literally) with the word Hello, for example.

  No, the author cannot do that, unless authorized so by Stack Exchange. That is, the author, being the copyright holder, can edit the question in any way they want and publish it on their own website, but they cannot post it here unless they conform to the rules of this site.

Your post is not a thing, and it has no concept of a single “owner” who could decide anything and everything concerning the post. In reality, there are multiple rights associated with the post that are held by multiple parties:

• You hold the copyright to the post content. This means that others cannot distribute the post or derived works without your permission. You are free to publish the post or its modified versions anywhere else you see fit (as long as you either own the means of publication, or their owner agrees with it, of course).

• Stack Exchange holds broad rights to distribute and otherwise use the post and its derived versions. You (the copyright holder) gave them these rights under the Terms of Service that you agreed with by posting the content here. You also agreed to give everybody similar distribution rights under the terms of the CC-BY-SA licence.

• MathOverflow the company owns the mathoverflow.net domain and rights to the MathOverflow name. They give Stack Exchange the right to use them under certain terms.

• Stack Exchange owns the servers that run the site. This gives them the right to decide what content to publish on the website, subject to legal and contractual obligations (including the above-mentioned user content licences and the agreement between Stack Exchange and MathOverflow). They delegate this right to users and moderators of the site under the various rules established on the site. Thus, in particular:

  If the author of a question on MathOverflow owns that question, then the author should be able to edit his/her own question in any way that he/she wants, including removing it completely and replacing it (literally) with the word Hello, for example.

  No, the author cannot do that, unless authorized so by Stack Exchange. That is, the author, being the copyright holder, can edit the question in any way they want and publish it on their own website, but they cannot post it here unless they conform to the rules of this site.