I think it tends to happen quite frequently on MDL too though, when people are becoming overexcited and just comment right away. The spoiler tag is such a cool and helpful feature, please uuuuse iiiit <3 I usually avoid the comment sections or forum threads or the like before watching a drama or before having caught up with all episodes if it's airing.
I accidently spoiled myself with 49 days though, after having watched the first episode I talked to the friend who recommened it to me and I basically guessed the "twist" and her reaction was too obvious, sigh :| Put it on hold, but I'll still watch it. And in the end, I'm not watching dramas for the ending - if the drama is really good, I don't care about being spoiled anyway.