[bobcorponoi]

I think the issue with correcting grammar online is that it diverts the conversation from the topic of the post. Of course this depends on the context but they might be excited about what they're posting about and seeing replies about their bad grammar or other off-topic things can take away from that.

If you can offer genuine advice privately, then you can but otherwise if you feel it might come off as rude or pedantic, then I would shy away from it.

[amichail]

If only we had a tech solution to this problem...

[bobcorponoi]

What's the tech solution? I don't want to assume.