It boils down to how you go about correcting them. If you kindly point it out from time to time, they won't get ticked off. However if every time they make a mistake and you correct them, they might take it as an insult to their intelligence. I once made a tiny mistake on spelling, and someone went off on me with a rant about how everyone he RP's with is always breaking his focus every time there is a spelling error. I'll quote him on this, he says mispelling is the equivalent to "A needle being plunged into the base of my neck."
Just be polite about it, otherwise people will just come to ignore you.
Just be polite about it, otherwise people will just come to ignore you.