Humans work better. HN is small scale enough that a moderator can come along, collapse the off topic comments and fix the title, and it's not an issue.
Seems like title cleanup is a good use for an LLM actually. (Not to remove the human option, but as the first smarter pass instead of simple stopword lists.)
An LLM burns through how much power, compared to the tiny Arc server? You could outsource it, of course... But then you have a third party dependency.
Then you have the problem that LLMs continually and constantly change words to be "simpler" and destroy the very sensitive meanings, especially words in tech. Like auto-correcting Fediverse into Universe. Or C into C++.