If all software by default use same moderation configuration, i expect it'll be less messy.
Who decides the default moderators in a decentralized system?
The default isn't configured on protocol/system level, but rather on software used to interact with the decentralized forum. But it means developer of the software have some influence to make certain moderator become popular.
Even if you took the current moderators, and used them to sort of define a moderation standard, you'd still be introducing centralisation there, since users would have to opt in on who they trust to moderate, the majority would pick who's the most popular out of them, retrospective to their actual moderation work.
That's true. It's proven by the fact most full node operator use Bitcoin Core.