@mhauden Privacy and security are probably the two biggest concerns users will have on any platform (or at least they should be).
Trust is the hardest part of the process because when you join an existing server it does require you to trust a possible stranger with your e-mail and IP address (the only PII stored on the server).
If you have any trust/privacy concerns at all, I recommend you run your own instance and have complete control over your data.
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@mhauden Getting to know the admin, even with just a quick review of their history online should help indicate if there are any red flags or not to help form your decision on whether or not you can trust them.
As for security, that's much harder to review and determine risk because it's all behind the scenes. I've been running server since high school (~20 years) and I do my best to keep things secure from threats I know about. The software itself is pretty solid, but I'm human so I do my best.