What I wouldn't like is anything that displays the date/time (beyond the said "Last here"), as I'm sure some people visit PM from work where they possibly shouldn't be doing.

IIRC, its not really tracked

Sure, posts have timestamps, /tell's, and votes, but thats about it

If you don't vote or post or tell, then last here is as good as it gets

Unless the access logs mention users ...

maybe "other users" leaves some tracks or could be improved to snapshot some frequency scores...

People come and go at their leisure, so ...

daily? weekly? monthly? quarterly? semiannually? annually?

saintly? devout? pious? observant? heathen? agnostic? enlightened? halo?

:)