On Lemmy the safeguard to mod abuse is instance admins. On Reddit this can take place, but rarely does. The only time admins on Reddit really step in is when mods are allowing illegal behaviour on their sub, or when mods are protesting against their own shitty behaviour. But on Lemmy it’s much easier to reach out to an instance’s admins if something is going wrong. Mod actions are all public, so you can create a post explaining what happened and it’s not just a “he said/she said” situation.
If they aren’t being responsive to feedback, the appropriate response is to start up a new community, preferably on a different instance. Or, in the extreme case, to block that instance entirely. You can even build a consensus to doing this with a “panel” consisting of…every user on the platform. That’s essentially how !tenforward became the de facto Star Trek meme community, rather than !risa, after the mods of the latter community were shown to be abusing their powers and the instance admins refused to take remedial action.