I have mixed feelings on this.
Volunteer mods are discouraged from it in my company. I feel their entire job is to be WITH the community, and it is kinda important that they truly be a part of it at all times.
Paid mods get two, a mod account and a plain one. They cannot use the second to moderate, but I do find their moderation and regular accounts are quickly linked. If I need to suspend a paid mod, I lock the mod account for a few days, which generally solves the problem during investigations.
I have four. My admin one, my mod one (allowing me a strictly moderator view) and a tester “member” account with no privileges are the main three.
I also have a fourth that is just for me to play on and has no permissions, though in the past this one was quietly and nonvisibly an admin account that was used to check up on members. After a security breach a year or so ago I removed permissions from my private account (nothing was compromised but I instantly realized just how bad that could have been). I don’t talk on that account, I lurk and occasionally trade with others only. It’s just for me to chill on without people asking me stuff. It also allows me to gauge the feel of the community when other staff aren’t around...
Overall, it can be a useful tool! Just one that can easily be abused.
Our revamp next year allows two accounts... not sure how this will change things, but one of the paid staff perks has always been an extra account, so mods will get three and I will probably have four or five. I’ll probably link my admin account with one of my two player accounts, so the other doesn’t attract attention and can continue to lurk. Trust me... lurking within my own community had taught me a lot!