On the edit issue screen, the comment entry field at the bottom says, "an optional comment describing this update". This makes it seem like the comment will be a revision history comment, to be shown in the 'Change History' tab on the issue.

Instead, comments which are made when you update an issue show up as normal comments. This looks a bit odd, when you consider that you end up with a comment stream like this:

• Issue description: "This is a bug"
• Comment #1: "I'd really like this bug to be fixed. You can reproduce it by doing steps 1, 2, 3."
• Comment #2: "Updating affects version"
• Comment #3: "This bug is really annoying. Is it currently scheduled to be fixed?"
• Comment #4: "Increasing priority of bug"

There's no distinction here between comments #1 and #3 which refer to the problem, and #2 and #4 which refer to changes in the issue. Comments #2 and #4 don't actually show the change that happened when the user commented – you have to switch to the Change History tab for this.

So this view kind of mixes up change comments with comments about the issue itself. I think you should consider making one of two changes:

• making change comments show up on the Change History tab, but not the Comments tab; or
• removing the comment field from the edit issue screen and the workflow screens where it doesn't fit.

There might be a better solution I haven't thought of, however.