Here is what the the announcement on discourse about deleting inactive users says:
Delete accounts that have never participated, are trust level 0 and have not been seen in 2 years
Discourse now includes a new site setting called clean up inactive users after days
this is set 730 days by default.
Once a day Discourse will find all user accounts that
- Never posted anything on Discourse
- If you posted something and then deleted it you will not be eligible for clean up.
- Have not been seen for
clean up inactive users after days
- Are trust level zero
This change is in place so Discourse default protects end users and removes emails of completely unused accounts.
If you wish to disable the feature, set clean up inactive users after days
to high number.
But we don’t know whether the staff here have set that setting to a higher number