Permanent vs temporary ban - is always tough choice to make for community builders and managers. My recommendation is that 'permanent ban' is always the last option when everything else fails.
To decide which type of ban you want to impose on user - consider the overall value they have added to the community. If their contribution is valuable and helps drive the community towards its goal; I'd suggest sending DMs or connecting over email.
If they do not listen or respond, and continue with their malicious behavior, send at least 2-3 warnings. Give them reasonable chance to change their behavior and adhere by the community rules.
If this doesn't work - impose a temporary ban for at least a week. Make sure that they understand the reason behind their ban.
Ultimately, if none of the above works; ban them permanently. There is no coming back from this stage.
So here's the overall decision making framework to decide between permanent and temporary ban:
- Step #1: Contact through DM or email
- Step #2: Send warning through your community platform or email or DM
- Step #3: Impose a temporary ban for at least a week
- Step #4: Permanently ban the member
This strategy works with most of the communities with lot of contributors. I've imposed permanent bans on users who simply joined the community to advertise their services and spam. I hope this helps.