Why are there time limits on comment edits? So I make a mistake in grammar or something, I type incorrect word, but I am allowed to correct it no sooner than 5 minutes later, where lots of people could already read it and misunderstand it. That's counterproductive.
The time limit exists because if you do go back and edit the comment, the comments that follow will no longer make sense. Chaos quickly ensues.
Moderators do have the ability to edit comments (without a time limit), and sometimes we'll clean up a comment thread that has some obvious misspellings and the subsequent confusion. You can flag a comment if you want to bring it to a moderator's attention more quickly.
Comments are transitory. They're not for adding content.
Questions & answers should stand on their own merits.
Minor mistakes in comments can just be 'corrected' by adding another comment.
You can always delete your own comments if you want to.
It seems to me that making comments perpetually editable would turn SE into more of a forum & less of a Q&A.
This doesn't answer your question, but is intended to clear up some confusion.
You are allowed to edit a comment you wrote within 5 minutes of originally posting it. There is no restriction on the number of edits, and the time since the last edit is not relevant.
After the 5 minute edit window, you can't change the comment anymore. You can, however, delete it altogether at any time.
Comments are more a historical/chronological discussion on a question or answer. In a real world discussion you can't go back five minutes and say something different. The same goes here to maintain the integrity of the discussion thread.
Edits are allowed for five minutes to let you correct the OOPS factor or to add to the comment.
But even then, they should be edited with care not to change the context of the comment since someone may well comment on your comment in the mean time.
If the typo is trivial let it be, we all make them. If it's an addition or major change add it as a new correction or addition comment.
BTW: If you do happen to delete a comment in response to someone else's comment, let them know, via a new, temporary, comment so they will know to delete their response also.
The 5 minute limit is site wide, not just EE. If your going to get it changed you'd have to go up one level and have a really good reason. Since the stackexchange community has already decided on 5 minutes, your unlikely to change it.
This is reason why they have a 5 minute limit: Should we be allowed to edit comments?
If you have to delete and repost.
Another interesting fact: you can tell if a question has been edited by the pencil icon by the time stamp.