Didn't realise this was being talked about. I don't really want to air all this publicly but I guess it's better than uninformed gossip, so here's what I have to say:
He was talking out his rear about things because he decided his mental illnesses (a few of which were self-diagnosed, the OCD for example, and the HFA - he just has Aspergers, nothing more, though technically aspergers is now just part of Autism Spectrum Disorder, which includes autism) made him a supercomputer (they don't, that's a big misconception) and made him unbiased (they don't - if anything it makes him a little more prone to confirmation bias) and he was using them as an excuse for behaving poorly and not following site rules, which they just don't excuse - basically a lot of what he said his illnesses did and some of those illnesses themselves was total hogwash, and even if it was all true it still wouldn't excuse his behaviour. He said he could tell the performance of a combination just by looking at it, but it was very clear he couldn't as he was arguing with things we already had solid testing on and the times he was right were always things that were obvious anyway (if he didn't straight up change his position and claim he was right all along).
I don't know why it started, I suspect a lot of it was simmering underneath for a while, but he was already on his last chance at that point (and not for the first time, either). He was suspended from posting - the committee didn't want to have to ban him, rightly so - and told to stop. He continued in private messages. He completely changed overnight and started going on about his illnesses and blaming it on them or whatever, as well as saying he deserved CM/Mod etc and just generally being egotistical.
I don't know how much of it was to do with me blocking him from sending me PM's because I got tired of him saying stuff like he was saying in public in private and generally being rude and disrespectful towards me and my friends, after I'd already blocked him on facebook for the same and asked him to stop via PM (I didn't block him on here straight away because of my responsibility to beywiki, and I figured he wouldn't abuse that - he did). He had already started doing the mental illness stuff in public before I blocked him anyway, it was a big part of why I did that in the first place - the discussion basically consisted of me trying to explain why it didn't excuse his behaviour (at least in my books, anyway), and when he started the supercomputer stuff I also told him that it wasn't true. Obviously, I'm not the best at keeping my cool and I was already very tired of him, but I stand by everything I said in that conversation, don't think I could've done much better given the circumstances. Eventually I got tired of the discussion, told him he had one chance to prove he understood what I was saying, he basically said "it's my illnesses that are doing this and hey how about you re-add me on facebook as I'm going to improve" - basically continuing to do everything I'd asked him to stop, so I blocked him
I gave him the second chance he asked for the next day (after I'd slept) and he simply continued to go on about his mental illnesses, which is exactly what I'd told him to stop, so I re-blocked him. Aside from that, you all saw everything else between me and him after I first blocked him, and you should be able to see that there was a bunch of stuff that I didn't get involved in that were major parts of his initial suspension - I did respond to some of his posts to try to prevent him setting a bad example, misleading others, and generally to try to talk some sense into him, but his suspension came after I stopped responding to him completely IIRC, and the stuff he was then banned for didn't involve me at all.
As Kai-V said, it was a lot more complicated than just being between him and I, ours just went public at times because I got tired of it and blocked him to attempt to make him stop and he continued and I don't have the most patience. There was a lot more than that, but I can only really speak of what I was directly involved in. He messaged a lot of people who have any kind of power on the forums, and has continued to do so.
Now he's making accounts to ban evade etc while messaging mods, as well as being a pain on my blog yesterday (I asked him to go away, he refused, so I blacklisted his IP and deleted the exchange). I really thought he was above this kinda thing but he's changed for the worse, I guess - seems to think he's the suave criminal who taunts the police, almost, but he's just being petulant and irritating. He's only become more condescending since he's been banned, if anything.
Don't get me wrong, it's a real shame to see it happened (especially this ban evasion nonsense) - my responses to him were aimed at making him stop before he got banned, but plastics will be fine - he was only really reliable for prices anyway, and I'll pick up the slack in plastics Q&A, and as for prices, we'll make do, I'll try to pick up on them, the price list is there, and there are other people who know them at least decently. As for beywiki plastics, what we really need is people who can get articles written to beywiki standards, which he couldn't. That's being worked on anyway. I hate to sound dismissive of him, he was still quite knowledgeable, but he was doing much, much more harm than good. The biggest loss is to the UK tourney scene, especially with HMS/Plastics Remembrance day coming up, and my heart goes out to them.
Other than that, there's nothing to really look into, he wasn't hacked or anything, he just lost the plot and is no longer fit to be a member of the community. He's been given plenty of opportunities to explain it but his explanations are always just him doing the same thing that he's been banned for.
I am legitimately upset to see this all came to pass, but it had to happen - the ban is for his sake as well, as he's making a fool of himself publicly. I sincerely hope he learns from it, but he's lost my trust and respect, especially as he's shown to me in the past that he can temporarily improve to get what he wants and then go straight back to doing the wrong thing again. If he stops acting like this and goes back to being relatively normal then I'm sure he'll be allowed back - I certainly have no issue with it as long as it's not just a temporary facade to get what he wants, but it is definitely not something that should happen overnight, especially given his post-ban behaviour.
To Ultra, seeing as I'm sure you'll read this:
Perhaps you should stop creating new accounts, and learn that you have to actually change before you'll be accepted back into the community. All of this misbehaviour really isn't doing you any favours - the issue is with us being unable to trust you, and this is the worst way to go about things in that case.
When you think you've changed enough (and I mean really changed, not "will change" etc), email the V and speak to her about it. That's how it works. Do some testing, take a break from things and try to get your head straight, stop bothering others, and get proper treatment (speaking from experience, one appointment is rarely enough for anything psychological and I don't doubt that you have aspergers, personally, which isn't something there's a drug for - it's going to take time and you need to be patient in general - trust when broken is not easily fixed).
If you actually improve, even I'd be happy to welcome you back, but you have to actually improve, not just say you will - I've seen you change temporarily just to get what you want before - as you said, you're only ever motivated by reward. If you want to help the community, you'll do what I'm suggesting.