At another science forum we had a situation where there were two mods and one of them went awol whilst the other was locked out.(Harold and Kalster)I was admin and mod at a science forum for a few years, and it was my impression that online moderation is not really like moderation at public debates, academic colloquies, tv round tables, etc. As James noted, we serve voluntarily and for free, and the primary carrot is getting to participate in a chat that we might help keep civil and on-topic. The firewall between participating and enforcing rules of discourse is really one of taking a vow to switch hats only when it serves to remedy an objectively identifiable problem of flaming, trolling, bad faith argument, misinformation, etc. Given that mods are humans who can enter into discussions where their own personal buttons are pushed, it is good to have a backup, i.e. another mod who can be called in to sort things out. Simply changing logins would not be sufficient in such a situation - a different pair of eyes are needed.
At the first opportunity Kalster banned Harold and nominated Markus Hanke and Dywyddr as admin and mod if memory serves me.
The owner pulled the plug sometime later.