[@Odin] [s]People that use the XD emoticon should be flogged.[/s]

There's nothing wrong with denying people mind, you're right that pointing out flaws won't automatically make one a better writer. Similar to the 'giving a man of fish versus teaching'. But they will inevitably ask "why?" When they do, I'd say would be fair to answer them. Though it would involve you pointing out what they spelled wrong, grammatical mistakes, cringey lines or stuff that doesn't follow the lore, or whatever rules you have put in place. Etc etc.

Let me go one step further, because I'm sure this happens to everyone. If you are part of a community of role-players, not a GM, but your with a chosen group and making/posting characters. You notice someone's character sheet is written just fine, but they have a misunderstanding with the lore, or just some things amiss, like a power that's not clearly defined. Do you think it's inappropriate to point it out to that person, so they can correct it? Do you just leave it to the GM even if you found it first? And presumably the GM is getting the first post written up, planning future plot details with the CO-GM's, whatever else. May even be something that was missed by the GM. (because they make mistakes too) and something like that a undefined power could potentially become a IC problem.

Doesn't it benefit more than yourself to @/PM that person and politely bring up the concern?