So now a typical member will be in two User Groups: Approved Registered (Priority value 4) as their primary group and then a second group to colour their username specific to the type of character they play on the site. All of these secondary groups that colour the usernames should have the same permissions and have the priority value of 5. The Approved Registered is meant to be a permissions blanket for all non-staff groups minus trolls and bans etc.
Also, just as an added precaution, I went through every node's permissions and changed those for the Approved Registered to allow everything I needed to allow that primary usergroup to have. The secondary user groups have the same allowances in their general group permissions.
Regardless, I'm having problems that I didn't have when I initially set up the permissions when we moved. It seems to include edit allowances to members' posts and conversations. I've checked the XF manual on permissions and I'm pretty certain I've followed it correctly but I must have gone wrong somewhere!
In short: where would you advise I start from to try and find the cause?