As someone with a Polish partner, who also fluently speaks my own weird minority local language (Irish), I'm more than well aware of pluralisation pitfalls; Irish may have one of the most complex rulesets, so much so that I'm almost certain it isn't represented in CDLR (possibly can't be). But I see the plural pitfall brought up in so many of these guide - I've always been curious about other unexpected/unintuitive pitfalls across languages out there. Would love if there was a simple reference of the most interesting (starting with plurals I guess).