I may never do so again if I can possibly help it. Not because of minor irritants - how few trains it's possible to compare at a time. (I cross-referenced with Deutsche Bahn's site, which was eminently useful when it came to train comparisons.)
But because of this: I was the lead passenger. I was the account holder. I was the card hotel. I was the person booking the trip.
But the confirmation and payment emails arrived to my email address addressed to the male traveler. Dear C.
P.S. I am feeling less wrathful and written a letter of complaint. If they do intend to fix this, if this is just an error in their system, then of course I would consider using the system again.
P.P.S. They wrote back promptly. They think C's name was listed as lead passenger, which is why the emails were addressed to him. Much as I am certain otherwise. But perhaps I misread field names? It's a good excuse anyways, and is, at least, gender-irrelevant, if customer service is correct.