@m4ng4 Technically what Streat said did not happen in the manga, so I don’t see why it shouldn’t be spoiler. It’s knowledge that a manga reader would be unable to gather otherwise (because the artist changed the events slightly).
If for example, a manga has X killing Y and then in its LN, X
tortures Y then kills Y. To discuss the act of torture with
manga readers would counted as spoiler won’t it? You don’t really know any of us here who might wanna read the novels later...
My rule of thumb is to spoiler-box anything that a typical reader cannot obtain from the medium they’re viewing.