The `lastVisit` field should only reset when visiting front page.
This may be tough to implement, but I've noticed that I have gone onto a specific thread without checking the front page. My last visit was reset and then later when I went on the front page the "last visit" line wasn't shown, even though there were new posts that I didn't see.

This might be alleviated if we implement proper read tracking (even if it is just a timestamp)