I don't think bb knowledge is a must. It's a bonus and helpful. My impression is MODS are suppose to be people friendly, who are here alot. Imo, i think a MODS duty is too try not to attack someone personally, but help with site problems. The MODS here are great.
I have encountered MODS elsewhere that were very rude, and i told them so. I have even argued with the head honcho of a site, (Bob Kolm).
On a side note, i saw someone mention post counts. They don't mean much to me, because it only takes me 3 posts of a person to see where they stand.