Fascinating discussion! Found the link to see what objections there might be to "someone else's," as in "I think this is someone else's pen, not mine! I don't chew my pens." Someone's else can never be correct - that would mean that someone possesses an else... hmm - what is an else? However, someone else is some person other than the speaker, the other interlocutor, or some person previously mentioned in the conversation or text.
Passersby! See - no red squiggle! If the freaking morons who create spell-checkers (and they're not morons, but they can be pains in the ass (hold on to that idea) think passersby is correct, it must be!
Touchdowns. Yes - but that is one word. Not touchesdown. See - red squiggle! But BrockawayBaby, your logic is flawed - interesting, but flawed. Let's look back at the discussion (I know - it's 8 months old - so what?). Eagle... said passers-by is a noun + adjective construction, but it is not. Neither is touchdown. By can be used as a preposition, of course, but also as an adverb. It answers the question "Where did the passers pass?" They passed by something, somewhere, etc. A touchdown is a similar construction - the score occurs when the player touches down in the end zone. Verb + adverb. But, the word touchdown is no longer a verb + adverb. It has become a one word noun, so of course its plural is touchdowns. Most of the nouns Brock uses are verb + adverb combos that have become common nouns. A push up is a form of exercise in which one does pushups. No red squiggly line!
But you COULD say, "After several pushes up the stairs, we stopped for breath; that's when that old refrigerator came sliding back down the stairs and crushed... " We gave the X several pushes! Up, down, etc.
So - work on this: I have two mothers-in-law, having been married twice. I walked into a room of mother-in-laws! What an odd convention! I'll bet you no more than a nickel, Brock-o-baby, that both are correct - and I really have no idea why... yet!
Someone else's turn! (Stupid squiggly red line!)