It is probably impossible to maintain operational security using discord

Discord collects who-can-say how much data about you and then gives it to whoever they like. It could be cops, it could be Koch-brothers funded activist groups. (i'll allow for the possibility that it never leaves their servers, though.)

There is also the problem of infiltration, where because everything requires invite codes, people develop a false sense of security.

https://unicornriot.ninja/tag/discord/

Unicord Riot showed just how dumb it is to rely on discord to organize any group or action.

Reddit isn't actually as left-friendly as we might believe, and they can destroy our subreddit any time they want

It's well known that t_d is filled with really awful stuff, but there are a lot of em and they pay for the server costs, so the admin team turns a blind eye. by contrast, they've taken a heavy-handed approach in the past even to jokingly saying "bash the fash".

Proposed alternatives

riot.im and mastodon. i'm open to other suggestions, too, but i have a strong bias against any solution which is not Free Software.