I tried changing all the phrases as well, to private message. I had to give up because there were literally hundreds of changes to be made and it was extremely tedious and absurd. There should be an easy way to change phraseology all at once. Like a universal search and replace function.
When I see PC...I think personal computer right away, then have to read the message and realize they meant personal conversation. I still say PM on my site. I don't like getting random PM's so I make it so only the people I follow on my site can PM me. I direct people with various questions to use the contact us page so my team can go through it and get things done faster than if it was just me since I like to just let those PM's sit until I feel like I have the time to read over a bunch of the nonsense that is sent my way and fix the ones that are truly problems; and since my demographics is very young (half my age) I tend to have to play "detention teacher" and make the kids stop their lil quarrels. I was never one to get involved in middle school and high school drama so having to deal with it now at my age, it just gets under my skin.
I use "Personal" message as opposed to "private" - private used to be okay when only two people were involved in the conversation (they weren't actually threaded conversations but rather individual sent/recieved messages), however now that other people can be invited into the conversations it is technically not private anymore.
I just can't get used to PC as a replacement for PM - it means personal computer the world over and just doesn't naturally replace the equally global PM (in terms of forums).