So is basically every platform. I do not have the capacity to host something on my own right now, and most people are on Discord already. Besides that, I've found a way to set things up so that we shouldn't have to worry about tripping over Discord's TOS.

I do eventually want to move the community to another (preferably self-hosted) platform once it becomes a practical option.

A number of ways, but here are the biggest ones:

1. We're narcissist-aware. It's like being tankie-aware, but much broader and more encompassing. Narcissism is unfortunately very common, and unless you have studied narcissism and narcissistic abuse tactics, it is extremely likely that you will be unable to identify them reliably. The lack of empathy that characterizes narcissism is fundamentally incompatible with leftism - they will always sabotage leftist organizations if they are present, even when they do not specifically intend to do so.
2. If you look at the formal study of fault-tolerance in distributed systems, you see that it isn't enough to simply have the right governance structure in order to avoid a state where the system (or community, in our case) is no longer able to function. The ability to reliably identify and correct (or remove) faulty actors is actually more important than the choice of governance structure for a community. A lot of anarchists believe axiomatically that power should always be decentralized, but fault-tolerance as we understand it would actually force us to avoid distributing certain powers to members who are not yet able to reliably identify faulty (and, in particular, bad-faith) actors. Of course, we still want to decentralize power as much as is practical, so we do our best to educate our members so that we can safely distribute power to them.
3. Looking at anthropology, we see that civilization has been a narcissistic endeavor from the start, and they are still in control of essentially all of it. This immediately implies that reform-based strategies can't actually work in the long run. It also implies that a simple regime change will not be sufficient to achieve lasting change. We've got to build a new kind of society which is able to fill the niche currently occupied by civilization as we know it - one which is actually designed to be robust to infiltration and subversion by bad actors from the start.