I found that in the database gl_commentcodes` VALUES (0,'Comments Enabled',(1,'Read-Only',(-1,'Comments Disabled'; existed. If I deleted the value 1, 'Read Only' then the update worked fine. I assume this was left over from an old version of Geeklog and had never been deleted.
So those are the ones you enter in the install script during the upgrade? In that case, everything is working as expected ...