I should round this 'irritate' up into one area. That is corporate industrialised catering, be it Costa, Nero's, McD, Pret, BK, KFC ad nauseam. I'll stick to local businesses in future. I can't enjoy food with a big angry knot in my guts.
Having a really disgusting shit in their toilets is very satisfying.
Especially if you don't tidy it up.