I think a subscribe link for each thread would probably be overkill. Most threads don't last very long, especially since there's a time-limit on responses.
ATM, simplifying the HTML and CSS, removing obsolete tags (like font) where possible. Also eventually themes and having the base font size be selectable, since not everyone is comfortable reading 10pt grey on grey text.
I guess these improvements will only affect people using the Anarki implementation of the forum? It would be nice if we could get some upgrades to the original arclanguage.org instance.
Specifically turning off the feature that disables replies on old threads, and probably switching to a most-recently-updated ordering scheme.