It's not quite auto-mark but if you use the "Forum Tools" drop down menu, there is a selection titled "Mark Forum Read" that does exactly what it says.
There is also a "Quick Links" feature that marks all forums read.
Not automatic by any means but the functions are there.
Kit (AKA Cranky Kong)
Total Total Impulse as BAR (2010): 8,784.59 Ns (Equivalent to a 72% M motor.)
The future sure isn't like it used to be. We were promised Jet Packs.