Hm ... problems.
Some of my useres cannot see the prefix-selection.
They so cannot open new threads in forums which have "forcecustonprefix" enabled.
I checked the permissions for every group and every forum. In the "user" table, the "Registered" group has "canusepostprefixes" enabled. In the "forumpermissions" table, virtually EVERY entry has "canusepostprefixes" enabled, also.
Doing the latter helped
many users, but some not.
What might be the reason?