status-declined (Jon Ericson)
The idea is a really good one. The problem is that making it work would require pulling in more features that have baggage we probably don't want to be burdened with. In particular, if you can edit comments, it's important that someone be able to track changes. The five minute window means there's not much opportunity to mislead people with edits. But if I can go back years later and edit a comment, it'll be easier to grief other users or sow confusion. At the moment, not even moderators can view comment changes; it requires access to the live database. In addition, it turns out that late comment edits are less tempting than you might imagine. I rarely use it.
Edit your own comments without time limit
Regular users can edit their own comments for about 5 minutes, then editing is disabled.
I suggest you remove that time-limit.
This is not a big privilege, but you did ask for a "micro-privilege".
