Yeah!s can now be disabled on a thread by thread basis by staff. For more details, see
the forum update thread.
Individual user settings are being looked into; both the ability to remove the button from your posts and to make the system invisible altogether if you'd rather not see it (as separate options). We'd also like to make official staff posts and actioned (warned/banned) posts unable to be Yeah!d, but individual posts have proven difficult.
Which brings me to this - I realize it wasn't your overall point, but if we do implement such a setting it'd likely be at a user level, not a post level. You'd either have them disabled across all your posts - even ones made previously - or none of them. This is mainly for technical simplicity.
Unyeah