Would it be possible to disable Captcha when a user is editing is own question/answer ?
At least for something like 15m after the post (to prevent mass change on someone posts if account is hacked).
I'm not sure why we should be any more or less concerned about "own post" (I can't see a reason to distinguish this from any other editing). The current captcha rates are discussed here.
Most edits (with some exceptions such as edits immediately after posting) can be rolled back / undeleted / etc - so if something bad happens, don't panic...
I do a lot of writing, and a lot of editing, and the captcha has never annoyed me. If anything, I like seeing it...wondering what odd combination of words I might get. Got a great one the other day, so I sent it in to Jeff and Joel for the blog. I find the good in it. It's keeping the site clean, and adding a bit of mystery to your interactions ;)