I just had a look :
Created 3 participants, one of them blacklisted at creation
Insertion is correct in database
then made change to set blacklisted from "NO" to "YES" for one participant, change is ok in database
Then I change the blacklist setting control
1) set not to show blacklisted participants -> change OK in database, but still display blacklisted participants
2) then set not to had blacklisted participants to survey -> still add blacklisted participants to survey tokens
All this test where first made with user #1 (superadmin) then with a other user with no "superadmin" permissions.
I had the same results.
I agree, this seems to bee a bug.
Where to declare it ?