Thanks! That's actually really valuable insight and seems to be a promising start for a interesting investigation
I'd even say that from a glance, EMACS ("W3" browser in it) seems like possibly hugely relevant application, actually. Will look into it.
If you really want to, you could check out Evolt’s browser archive:
https://browsers.evolt.org
It‘s got over a hundred ancient web browsers. I suspect none of them support SHORTTAG NET though.
Good idea. I remember I have done some research about this in the past when I tried to trace historical arguments for the infamous "should there be a space before slash in void tags for the best compatibility"
discussion, but didn't get much far then (https://stackoverflow.com/a/30880386/540955).