User blog comment:DaNASCAT/Introducing New Moderator Opportunities For Community Administration/@comment-25739558-20160114182929/@comment--20160115051043

We had discussed the possibilities of removing or migrating the Chat Moderator group. But Chat is a very highly used feature on many communities and sometimes most of the community's activity happens there. Thus the Chat Moderator right has been highly debated and valued on a number of communities and it didn't feel right to simply rid the position due to the high use. Migrating it didn't make sense either because of all the extra rights Chat Moderators would suddenly have as Discussion Moderators and that seems like it would not be what the vast majority of communities would favor happening (at least automatically, without any community review).

So, since we were keeping Rollback as a small (in scope) Content-area group, it made sense to grandfather in Chat Moderator as a small (in scope) Social-area group.

Re: Blocking, that's a very serious right that is best kept to just admins. Part of the purpose of these mid-level Moderator groups is to let a user get a feel for wikia management without putting them in positions that they are either not prepared for or the community does not yet trust them with.