I think that N4H's Canon Watch thread is a better solution than transcripts.
There is a small problem there.
There have been cases of people cloning Buffy-Boards to make their own sites. Now if you happen to be the person who's put a lot of effort into making a board special it's going to be irritating to see your hard work replicated. It's not really illegal, just irritating. Irritating people can come back, and bite you in the ass.
That particular problem is one easily dealt with by good manners though. If you saw something you liked at a website, and wanted to use it, it would be good manners to contact the administrator, and say "Hey, I like that idea you have where you do such and such. I'm thinking of doing something similar. Would that bother you?" If the person was at all reasonable, something could be worked out.
In that particular case it shouldn't be a problem, because the idea isn't even original to this site. Basically Canon Watch is just a review with photo-clips for illustration of points. That's done all over the internet. (Calling it "Canon Watch" might earn you a scowl though).
As far as that particular thread goes, is it legal? I'd say yes, because it fits the definition of Fair Use.
The easiest way I've found of describing Fair Use is with this YouTube video.
YouTube - A Fair(y) Use Tale
But back to your transcript question. Is it illegal? Hard to say definitively. Nobody's done it, so it would have to be answered in court. My best guess is your chances of winning such a case are slim to none though. You'd have to be rich to afford a good lawyer to even try.
So what would the consequences be, if you did it? My best guess is you wouldn't be sued. I would expect them to ignore it, until a time they saw economic potential in the idea. That's what usually happens. In that case you would most likely be served with a takedown notice. If it came down to that there's 2 ways they might do that. They might contact you directly, or give your ISP a DMCA takedown notice (if you're American). If they wanted to make a point, they could demand you take down all related graphics, and written materials to which they made a claim of copyright ownership.
That idea is non-commercial. I doubt they'd put their full legal weight behind any possible repurcussions. They get a little pissier if you try to make money from something they hold the copyright for. You might want to read the thread linked to below about the guy who was selling T shirts with a reference to Serenity.
The Serenity T Shirt Debate - Buffy-Boards