Having seen the damage a lower-end cassette can do to a Hope freehub, does a thin SS cog not do even worse? Are some better than others at avoiding damage?

Replace the aluminium Freehub with a steel one.
I use a wide base Velosolo cog on the steel Freehub and there using a mark on it, not sure the aluminium one would be the same.

Used a ss cog on mine for over a year now. No damage.

I had a Surly cog on a Hope hub with a steel freehub and had no issues over 2 years of use.

I had to replace the cog, chain and chainring in that time; but the steel freehub was fine.

Wide base 16t cog on a Hope aluminium freehub is fine for me.

I’ve got a wide a wide 16t on mine, and it’s fine although I did trash the free hub bearing this week, it was pretty well used! I guess the sort of terrain we ride would make a difference? I mean, in Thetford I don’t spend much time stomping it up hills!

Got slight cutting with a thin 22 on my pro 3 sp hub in 24 hours use at puffer

Changed to a wide base 16 after that and no further issues in 3 years

I use the on-one groove armada cogs on Hope hubs, not had any issues.