I still think it has strong normative value. Maybe at some point when norms have become firmly established these comments will be pointless and spammy but I don't think we're anywhere close to that point yet.

A lot of blogging is essentially self-expression and that stuff won't be taken over by LLMs (it defeats the whole point). Other blogging is done with some kind of sales/promotional/brand purpose and the extent to which LLMs will dominate this will depend on how we as a society react to it (see the AI art battles) since if people react negatively to it it becomes counterproductive.