If I write a post I should be able to edit or delete it at any time. Example: I posted, and then my modem choked. When I got it reset and connected my post would not let me edit, so I was not able to make corrections. That's pretty lame from my point of view, especially when posting on the Internet creates a legal document attributable to the author. So even if someone (else) replies - the author should retain full control of the document (post), not the software provider, until such time that disposition (destruction) of the document is legal from a records management perspective.
Unfortunately, nobody short of the owners (and perhaps JamesR) can do anything about this - even then, it may be an inherent part of the forum software and not something that can be changed.
How much time passed? Typically, entries should be editable for - I dunno - maybe 15 minutes or so after posting? If legality and accuracy are an issue, this can trivially be mitigated by writing your entries offline and proofing them before posting. I often do this when writing long posts.
Quora allows editing at anytime after posting but it is not really a discussion forum. More just ask and answer various odd questions Please Register or Log in to view the hidden image!
Isn't that why this section, to ask the people who configure the software to have a look at it. Steam forums, for example: I can delete any of my own posts at any time regardless of who replied to it. Or, I can just change the title, or change the wording. Why, because in the United States I retain the rights to content that I create. I give them a license through the TOS agreement, but they can neither forbid my access to it, where they can grant access, nor can they brand it as their own (although I've seen companies that do just that with OP's content). I've worked on forum software, and it is a pain, but just because it's a pain does not mean that I can disregard owner rights to the content they post, especially regarding the owners ability to remove content while it is being displayed to the public.
There can be a problem with unscrupulous behavior that way, though. If every response to a post isn't quoted, (and stored in the database), the post originator can edit and say, "Who, me?", to any responses... Alternatively, the responder can edit the quoted text. I limit edit time to 15 minutes.
I run into formatting issues, as well as typos and flat out errors of mistaken thinking, that can take more than a few minutes - and I don't always catch them in time as is. It's embarrassing to have a dumb mistake permanently on display, but it's just a yak forum - no big deal. Look who else is here.
When you sign up, you agree to the terms under which you post. In doing so, you waive certain default rights - you give them permission to own your posts. And since you know that your editin windows is limited, you will certainly proof all your content offline before posting it.