Thanks for the suggestion of Poeschengband - I've given it a go and it seems interesting, though confusing. I get the impression there's a virtue system, but it doesn't seem to be documented anywhere? I'm playing a Paladin, so I'm trying to avoid attacking sleeping monsters and losing virtue, but there doesn't seem to be any practical way to wake up monsters before attacking (I'm missing Crawl's 'shout' command here).
Also, is dual-wielding documented anywhere? I tried sticking a short sword in my left hand to go along with my tulwar, but I seemed to be performing worse so I went back to solo-wielding.
I
think the help files in game (or maybe in the game directory) give something on it. Checking, it gives at least a bit in help -> creating a character -> proficiency levels. Something else shows up in the faq part of the help files.
Dual wielding, most classes start off with zero proficiency in it (to check proficiency, hit ~, and then go to... the second page, I think. It'll have something about that sort of thing under the misc one), which means the penalties are faintly ridiculous. Can't quite remember how to check how bad it gets in poscheng, though, but it's mostly just a fairly massive (like -50 or something at the very beginning, maybe worse) penalty to to-hit. After you use it for a good while, you'll start getting better at it and the penalties will start dropping and, I think, eventually go positive. Weapon proficiency helps there, too (since it boosts to-hit for the specific weapon), as does anything in general that gives +hit -- blessing scrolls and whatnot are particularly nice on that front, once you've got a bit of gold to burn. If you don't start off with anything in it, it's probably a good idea to hold off for a while on training it, or at the very least keep something to swap/take one of the weapons off when you're fighting anything that's even the most remote of threats.
Does seem like they removed angband's shout command (it's usually shift-x, iirc), though. I
think you can get a similar effect by just waiting nearby until they wake up, particularly if you're not very stealthy. Later you should be able to find aggravate equipment or whatev' (lighting effect'll do it to, I think, providing they're not light sensitive) and go things that way if you really want to. Probably stuff I'm forgetting, too. Never really bothered to care about alignment.
Insofar as I can tell, no, the virtue system isn't documented. I don't recall what/if anything it really does, either*. There's a birth option to turn it off, and as near as I've noticed checking ladder dumps of winners and such most people just don't seem to bother caring about it. I'd probably just turn it off if you don't want to bother with it. Never really noticed it adding much to the game, s'mostly just there for flavor.
*Though looking into it a bit, it mostly seems to be a very small effect. Few percent on spell failures if you're casting conflicting aligned spells, some monsters being slightly harder to tame/control that sort of thing.
E: That said, if you can stand machine translation,
this looks like spoilers for one of the other heng variants. Virtues are on the left list of topics, near the top; the effects would be mostly the same in poscheng. Not too hard to puzzle most of it out, checking over it.