I’ve seen this initialization used several times in connection with the SDMB. It apparently stands for some kind of transfer protocol. What kind? :confused More importantly, what does it actually mean? I mean how would that alter SDMB,etc. Excuse my ignorance, but that’s what this board is out to fight.
It stands for “Punch The Pole”. You may remember those “shock the monkey” irritating web banners. The SDMB had a similar webvert, but the ill-advised campaign portrayed a drunken person of the polish persuasion who was stumbling across your screen, and if you managed to click on him with your mouse you got a free Straight Dope T-shirt.
Due to protests from the Polish ambassador and a letter-writing campaign organized by the Krakow-Chicago friendship association the campaign was shelved. Nowadays we prefer that those initials not be used at the SDMB.
OK, what does it really stand for? 
Pay to post, i.e. the possibility of the SDMB charging a subscription fee.
You mentioned transfer protocols; PTP can stand for Peer-To-Peer (or sometimes Person-To-Person) networking - a setup where computers are networked together without the specific need for a server.
But that’s not what it means in the context of recent threads here.