Apostrophe rules are scatterbrained, but I'm not sure how high they be on a list of grating flaws or kludges in English. I might not even have made them a separate list entry; they're a subset of homophones, and many other homophones are more detrimental to clear communication. Non-phonetic spelling rules make it harder for everyone to learn to read. Irregular conjugations add unnecessary and illogical hoops to jump through before anyone can even speak without unintentionally signaling low intelligence. Hell, I used to think of I/l/1 as a programmer's problem until I discovered that toddlers stumble on the same unnecessary ambiguity; at least programmers get to choose their own fonts.