1) That's a good point, but I think if anyone was blatantly forging logs, the other party would probably object, strongly. We'd have to then consider the possibility and weigh whether we could accept the contested evidence. If they're not disputed though, then I don't see why we couldn't use them. I am unaware of any use of IRC logs in any Magistrate cases in the past (until these two anyway), but I cannot speak for the Titans.
2) There are many facets to the Social Contract. This question would take a while to answer, and I'm not sure our approach would always be consistent; there are a lot of circumstances that could change our approach from case to case. For example, if you're genuinely suspicious that someone is cheating and you privately consult one other player to see if they've noticed anything odd, that's probably fine, once, provided that the context demonstrates that you are sincerely only interested in gathering information. On the other hand, if you contact 15 players privately in succession, it starts to take on more of the character of a campaign of slander since every individual player you contact is now considering the possibility that the accused is a cheater, which certainly could result in negative consequences for that person. There's no quick and easy answer to this question, but if you're looking for a guideline, it would be just don't talk to other players about your suspicions. Period. Report it to the Titans along with your evidence and let them sort it out.
Regarding personal information, that clause applies to the information gathered by the Battlemaster game associated with your account, namely your real name, email address, time zone, etc., and prohibits other players from sharing that information (as seen on each player's user page if they have chosen to publish it) with any third parties. It is not, so far as I am aware, intended to apply to anything else since no other personal information is currently collected by Battlemaster itself. For example, IRC logs are not collected or stored on a Battlemaster server. Whether IRC logs should be governed under this clause or some similar protection is an interesting question, one I'm not totally prepared to answer.