I respect your comment, but I'd like to address this. Constructive criticism is perfectly fine. Only destructive or constant criticism is truly rude. Another thing is, society considers it only acceptable to judge someone or something when they ask for it, or when they deserve it, which is a decent thing to believe.
Criticism, be it constructive or not, can still be rude. Additionally, there is a point when an opinion or even the opinion of several are still based on preference. Recently, I have been scrutinized for my flowery writing style. So what? I'm still grammatically correct and there is a huge crowd that would rather read well-constructed, flowery sentences than dull, neutral descriptions or statements. That is preference, collective or not, and it is rude to push your preferences onto others. Before making any criticism, you should be aware if you are criticizing an actual, detrimental issue or just a personal one that doesn't need addressed whatsoever. Also, the purpose of asking permission is for etiquette. Not only is criticism on any level an often sensitive issue, using a polite, well-mannered attitude is the best way for toning down the negative issues with it and reaching the desire goal.
Oh, and to anyone who attempts to be judgmental or criticize you in their very first message toward you can fuck off. That's rude as fuck. Saying "you show potential if..." or "if you improved this" really just merits you a whole bunch of social animosity that you generally deserve.
A lot of people don't come here to 'improve' their writing, but rather to play a game or indulge in escapism. It's kinda like you're having fun playing casually Sonic and exploring the level, then someone walks into the room and starts telling you how you could have gotten a better time. That's still unwanted criticism.
Also take note a lot of people don't take criticism very well and another lot of people doesn't give criticism very well.
That's another excellent point. Some people just plain don't give a fuck, and kudos to them! There is no point in criticizing someone whom doesn't want nor appreciate the gesture. That, as a matter of fact, is when it becomes rude.