No one is asking that we reject all prose with emdash. Not all emdash-users are LLMs, but many LLMs are profligate emdash-users, so adjust your priors accordingly.
Secondarily, I think there's a part of the discourse missing: the presence of a syntactic emdash in a sentence on the internet is not itself a strong signal of LLM-writing - but the presence of an actual emdash glyph (—) should raise some eyebrows, esp. in fora that aren't commonly authored in rich text editors (here, twitter, ...)
Secondarily, I think there's a part of the discourse missing: the presence of a syntactic emdash in a sentence on the internet is not itself a strong signal of LLM-writing - but the presence of an actual emdash glyph (—) should raise some eyebrows, esp. in fora that aren't commonly authored in rich text editors (here, twitter, ...)