I installed Grammarly on my imac as I often had issues with grammar on my business page. But on another forum that was really full of odd miserable people as soon as you bit at their comments, grammar was their only tool for come backs.
Then I noticed on lots of other posts they would correct grammar all the time. To the point it was more like an English forum then a bike one.
So, although at times offering some help seems a good idea, I think it can be patronising. There will be people who struggle with it and may limit posts in fear of being picked on. And no, I don't think they would feel they're being helped by correcting them.
Just my opinion of course.