If there are vacancies for moderation positions, moderators are asked to present people they'd like for that job and we list their potential candidates and post opinions about potential candidates listed by other mods (there is kinda off discussion). After the list of several candidates is created it is reviewed by higher authority (global mods and admins). They choose one person from that list, taking into account moderators' discussion, and ask him/her if s/he want to be a mod.