I had no idea startling was personally offended because none of his comments were anything out of the ordinary for that vein of mock offensive humor
Seriously? You think it's plausible to interpret
gwern, "deceptive" is a pretty terrible word to use for trans people.
and
gwern, what a disgusting thing to say.
as humorous mock offended responses? How much clearer do you want him to be?
Typically when you want to break out of a language game, you use standard indicators like 'no, seriously' or going to personal messages (as I believe someone has already suggested that startling should've done) or anything like that. Like when you are roughhousing with your brother or sister and they say 'that hurts' and you continue since, well, you're roughhousing, and then they say 'no, seriously, that hurts!' 'Oh, whups!'
There are all sorts of things like that in ordinary social games; although taking things out of context and as literally as possible...
If it's worth saying, but not worth its own post, even in Discussion, it goes here.