I've noticed that after editing a comment, I'm unable to edit it again. Is this intentional or a bug?
The reason for that is that you tried to edit your comment too late. So we can say that there is an expiration for such edit. After five (5) minutes you are unable to edit it. If you would try to edit within five (5) minutes more time, it would work. Guaranteed :) Also, there has to be at least five (5) seconds delay between two edits. So within five (5) minutes you can edit so many times as you want, but at least five (5) seconds between such edits. I hope this helps you to understand the rules that apply for editing. :)
Comments may only be edited for five minutes. No more than one edit in five seconds.