> Making them configurable from site to site is really dumb, because it would create an unthinkable usability mess.

Why? Let people figure out things themselves, if they are so keen on changing their keywords. They can get together in their own webmaster threads and figure this out. I don't see why this should be solved here.
Of course I think this is a dumb idea in the first place. Nobody needs to know what fusianasan and sage are. Write a FAQ with two sentences about it and/or let your oldtime users tell newbies. Two frickin' words, and you people talk about it as if it were something like making up a new system of romanization!

> Then why not simply boil it all down to the comment field, with trigger strings for inputting the name, e-mail, sage, ID:Heaven, and fusianasan? You can get a lot more minimal with the current interface.

That's a bit too much. You want to talk about sage and fusianasan in the comment field, not trigger it with it.
I suspect you are joking here, though. Design is about what you can take away and still remain optimal conveniency/efficiency on the user part, not about taking as much away as you are technically capable of.