Agree with Lougle.
Disclaimer: I am Alouiseg's friend in RL. However, I hope what I am about to say would be no different if I didn't know her from Adam. I will not take sides re: the whole Twitter thing as I didn't read it so I cannot know who was justified in doing/saying what. But I have some thoughts and observations on what has gone on since.
Posie I can't really see the point in your leaving whatsoever now. I assume you feel vindicated as a result of this thread. You could have reported any PMs you felt were below the belt quietly and privately, but you've gone down the attention seeking flounce route, and eeked out a full four hours whilst knowing that Alouiseg's identity was being drip fed, and speculated upon, which was clearly your intention all along. You should have just named her in your OP and be done with it. So given that you have achieved what you wanted, and got loads of sympathy - why leave?
Re: The PMs. This is a minefield. We will need a whole raft of best practice guidelines about how/why/when we can PM people, and what we can and cannot say in future. We all know we use PMs to bitch about one another from time to time - but taking someone to task face to face is is off limits on PM, whereas blatantly rowing with them on the open forum is not? 
If I make what is deemed a personal attack on a poster as a one-off, the post gets deleted, end of story. Alouiseg has made what presumably constituted a personal attack by PM, because she felt that what she had to say might compromise Posie and should be between the two of them and not for all to see - and she appears to be banned.
Can some arguments not be put to rest privately then? Is it obligatory that whenever a serious difference of opinion erupts, it must be played out in one big gladiator's arena for all to see? We really should know for future reference.
And on bringing up old threads: I see no harm in it. In RL we need to stand by things we've said or bear the consequences. Our friends' memories are not wiped clean the moment we walk away from them, and it's no different with online friends. We are entitled to change our opinions, of course, but we will piss off our friends and garner little respect if we have no consistency in our stories, gloss over facts, conveniently forget that certain conversations ever happened, or just be a hypocrite. It's tiresome in RL and it's tiresome on MN. (not aiming any of that specifically at Posie, just making the point that we should be able to reference things people have said in the past - just as we would in RL.)
I know it may be bad form to drag up people's pasts into threads when it is not entirely relevant, but sometimes if their memories are annoyingly short, and they are spouting inconsistent crap, they need a polite reminder. Again, I did this myself just the other day. So. What is it then - we can do this - so long as it's not by PM?
I think unless you were fighting your corner on the Twitter argument and have followed this the whole way, then saying publicly you will ignore Alouiseg now as a result of Posie's flounce is a bit childish and smacks of playground gang mentality. There are always two sides to every story and so far you only know one. If you want to avoid any poster because you find them objectionable then it's easily done - I do it all the time. I just don't feel the need to inform you all of who they are by way of a list.
Last point - thesecondcoming - your remark about Alouiseg's politics were irrelevant, childish, bitter and nasty.