There's a certain person that I would like to continue seeing their forum posts, but not see their uploads.

I noticed that user:faux-pa blocks posts, but also blocks forum posts. Is there another tag I could use?

There's an option in userprefs to exclude forum posts, comments, Dmails, and blips

Unless, you have any of the above enabled for other members (i.e user for person #1 but not for person #2),
then that's not currently possible tmk

You can probably do it via clever tagging:

//Block all uploads except forum/comments:
user:chaser rating:s
user:chaser rating:q
user:chaser rating:e

//Block all forum/comments except uploads:
user:chaser -rating:s -rating:q -rating:s

Maybe a meta tag modifier in the future so we can do type:comment, type:forum, or type:upload