Interesting. I had no problem reading that (except for 'arsing' which I thought I'd misread). The ability of the brain to pattern-match upside down is amazing.

Fascinatingly, I read your comment first, then tried to read the upside down post — the only word I had trouble with was arsing.

Sight reading is really fascinating.

Varies by person. I'm nearly 100% incapable of reading upside down text.