We store three major categories:
1. Server unique data like the community's display image, name, and gross number of members.
2. User-Server relation data like specific information about message activity, when the user joined, roles, nickname, permission level, etc.
3. User unique data like profile picture ID, whether they registered, date first seen, privacy settings, and more.
We run cron-jobs to measure different per-community data points:
1. # score of User->User relationships, at a one week resolution
2. # of User messages, at a one day resolution
3. # of Server messages, at a one hour resolution
4. # of leaves and joins, at a one day resolution
5. Banned users aggregates
You can request deletion for user data or complete wipe of server data through our Discord server ticket - sorry, we're working on this (we don't have a pipeline for this yet). If you just want us to not collect data on you, you can run !opt-out in any community and we'll stop tracking specific data points about you.
Yes, if you remove us from your community we'll have 30 days to make sure it's completely gone. If you add us back before then, we won't end up deleting it :)
Unfortunately, we can't use global opt-in and still provide a compelling service. We actually do use opt-in for some other features, just not when it comes to the main per-user collection that we do. We understand that privacy is important and you should talk to your community leader about what services they use.
One thing you should know is that if you're in a public community, assume your data has been mined already since something like this takes only a couple seconds.