Bad writing is like poison, if you take a small bit of it every so often, you can build some resistance to it. Like I said before (and I don't mean this as a personal attack), pushing your own standards on others is a tad unfair way to go about life.
It's like an accountant saying that they can't tolerate a cashier that's slow to do her job. It feels quite a bit of a snobbish conduct even when the person in question is an expert in their field.
Writing skills is one of the last things you can choose to bitch about.
Nah, of course you should share your opinions to your heart's content. (Hopefully no ones writing is that bad. Not even sure "My immortal" cuts your lifespan. ;3)
I often fail to read as much as I should. (I mean outside material, I read everything in my roleplays, I assure you.) And reading, good or bad writing is still a helpful tool for improving yourself.
I mean nearly every complaint given comes from some kind of standard, that you could stretch into saying it's a selfish desire. Though, I'll say in regards to myself. (or really anyone who does so.) Sharing your own personal desires, isn't the equivalent or related to forcing anyone into doing something. Not everything I complain about presumes those must follow those words, in fact I'm nearly exclusively laid back as a roleplayer.
But I also think it's perfectly fair. Judgement is done by everyone and everywhere in life. I don't think it's unfair to have standards either. If one didn't have any standards, would GM's ever be allowed to deny character sheets or certain things they disliked? Is it always unfair? Maybe it seems that way for the person who wrote it. But as long as critique remains constructive, it's always a necessary part of improvement. Some may not roleplay for improvement, some may just do it for fun. But assuming everyone will take an idea of someone else's frustration, negatively, is a false equivalence.
I think in a roleplaying thread specifically meant for complaining, I think the best possible thing you could post about, is a richly detailed description of something in writing or roleplaying that stresses you out, while providing examples of how those things could be fixed. At least that's my own two cents. ^_^