I don’t know where you got the impression that I said that if something is an allophone in one language it’s an allophone in all languages. Jeez!

I think that this impression is mostly from the fact that your post doesn't make any reference to English (or another language lacking the distinction), so people are incorrectly associating what you said with Korean instead, and incorrectly assuming ignorance.

I don't think that people would misread you if the meme said

"When you have to distinguish two sounds from a language that are allophones in yours". // 살 and 쌀 sound the same for me!

That said, I fully agree with you that people aren't spending enough time trying to understand each other here.

Ah, thanks for the info (from another comment) on Korean rendering some English /s/ as one or another consonant! It hints that English at least comes close to the tense-S in some situations.