This is very trivial but i'll report it anyways
I just noticed if you are viewing the list of users online and try to jump to a thread they are posting in by clicking the link to the thread in the "action" section, you'll receive a 404 error.
The link DOES work if their action is "viewing the topic" but it 404s if they're "posting in topic"
This is because there is a "?" missing in the url between "php" and "topic"
Fixed!