I don't think "deterministic" is the right term to capture this concept. An if-statement which bans posts containing a political phrase would be 100% deterministic, or one which prioritizes anything from a username on a list.

> On-topic-ness is deterministic, if a bit fuzzy.

If you permit that exception (even for good reasons) then it reveals how the original "algorithmic elevation" is too vague and unenforceable.

All someone needs is a ToS footnote like "this forum is provided for truthful international news and engaging with $COMPANY in a positive way." Poof, loophole. Anything the moderator (or moderator-algorithm) decides is "untrue" or "negative" becomes off-topic and can be pushed down.