I feel like "I'm insisting that this is worse than you will admit" only makes the hurt person feel worse and weakens their inner defences (which might be all that's holding them together!). To me, in most instances (but not all!) the kind and supportive thing is to take one's cues from the hurt person about how much comfort they actually want.

I entirely agree with this! Though for me that has nothing to do with how I, the reader feel about the characters and their pain. And the characters are allowed to have non-ideal reactions to things, too, you know?

(It hadn't even occurred to me to think of this in terms of h/c, tbh! Fascinating.)

But in general, ZYL's fraught reaction does make the whole thing worse for SW

Yes, 100% agreed on that, too! One of those non-ideal reactions, but he wouldn't be ZYL if he didn't react that way in that moment.