There is a 5 minute limit on editing comments. Perhaps the idea is to keep the flow of the thread faithful (to avoid distortions--or even manipulations--of a discussion).
However I happen to be quite prone to small errors like typos etc. An error can be small, occasionally just one letter, but the effect can be frustrating. Thus I would post a "new" comment which would be a corrected copy of the eralier one, and then I would remove that wrong one. This however gets tiring.
Thus, if possible, I would suggest that a comment can be edited as long as there was no new activity by others in the given thread. Once there is any new post or edit of the question or an answer or any new comment then editing of the given comment would be off. What do you think?
By the way, the removing operation would still may endanger the integrity of a discussion--I hope, no such things will ever happen. I am talking about the general principles in a theoretical way. The rules should be optimal.