Tuxide, it saves confusion, simple as that. If you wanna roleplay "in a vicinity", use the main tab, keep guild OOC. Good example is, way back when I was in the Feline's Lair, we would swap between OOC and IC chat in the guild tab. We were all speaking OOC, then suddenly a new member joins, and I typed in something OOC. Just then, everyone yelled at me "RP!!!!!! RP!!!!!!" and caused a great deal of confusion that heavily ticked me off.
Just don't do it, IC in main tab, OOC in guild chat. Saves a ton of confusion and "character ruining" as I call it.