if the forum doesn't ban their low-quality posts
The forum should ban them (not just posts, ban the shitposters on sight) though, when they spill over to the rest of the forum. Ignoring sounds good in theory, but it requires compliance from everyone, otherwise it's pointless, and such compliance is never going to happen.
I was going through Bitcoin Discussion and other shitboards a few times and reporting all the shitposts (you know, the one-two paragraph garbage about nothing) and problem is not just shitposters themselves but also presumably smart and rational users - some of them with e.g. ChipMixer signatures if that means anything - responding to those shitposts. This perpetuates and legitimizes all the mundane and dumb shit posted by 0-merit copy-pasta Google Translate drones. Can everyone stop doing that? I don't think so.
I don't particularly care about someone who never leaves the Bounties board, they can all rot there.