Commit comments don't solve everything. There's always a chance they may mislead as much as they help - especially when developers are angry about having to enter them. Try this: consider them like a bread crumb trail in the woods or a mountaineering waypoint or tracer bullets. Done right, they can outline an otherwise confusing path.

Don't make a big deal out of them. Be honest:

• "Edited spacial index entities, Daos, and UIs to handle feature X"
• "Incremental check-in for feature request #1234 and bug #5678"
• "I broke the last build. These are the files I missed."

Keep it short and "big picture". If possible, refer to an issue number in your feature/bug system. Some version control UIs include a field for this sort of thing.