1) Trojie and Pads' missions ca be found on a dreamwidth journal.
2) I am unsure what you mean by that, please elaborate.
3) You're welcome to put them on the wiki.
4) And as to your issue, you just explained it right there with those quoted portions. "We want to see whether you can write well, basically." Flaws in pacing, a lack of depth of character, and no real development within the story indicate a basic inability to write. We- the PGs- are not here just to filter out basic SPaG issues. When your own writing has the same problems that we nail as being elements of badfic, spelling and grammar or not, it means that you shouldn't have permission yet.
I can't speak for the people who got permission who you think are lacking in characterization and pacing, but as Araeph put it in one of desdendelle's earlier shots at getting permission, PPCers shouldn't be just 'entry level' writers. We need to know about writing and how it works. If we don't, we can't identify the unintentional humor that can be caused by use of questionable sentence structure and word choice. We also wouldn't know how to improve our own works.
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Beyond that, there are so many spin offs now, that we should be trying to have better quality for new writers. What incentive is there to read their things if the writing is mediocre, and the only thing they have a handle on is grammar and spelling, and their characters aren't interesting, and the way they write is dull? There are other, better things to read, PPC or not.
The important element in this isn't Spelling and Grammar. If anything, that's just a surface matter. I can't speak for other PGs, but I'm more inclined to give permission to someone whose story and agents for their request are legitimately interesting, and they hit the right spots as far as humor goes, know how to pace their story, or reveal or do something that makes me want to read more, even if their SPaG is off, than someone whose SPaG is technically perfect but has a story and characters that are the written equivalent of cardboard: Flat, without contrast, no change, tastes like cardboard, and soggy when wet.
SPaG can always be fixed, either when they learn it themselves- if they don't have any learning disabilities that get in the way of it- or with the help of a beta.
No one can help with the cardboard stories and characters, short of rewriting everything to the point where the original author's work is all but gone.
Beyond the issue of SPaG, there have also been incidents where previous PGs have also denied Permission on the basis and/or concern that the person who gave the sample would go against the spirit of the PPC on various items, such as lacking participation in the community or not getting along with it and its values (for example, if Nakkel decided to ask for permission, there's a higher chance of HQ being invaded by corgis than him getting permission due to his trolling nature that usually involves him bashing on things and people, which isn't PPC or cool at all) or trying to make the PPC grimdark, depressing, and utterly serious without the odor of humor to it at all.
Getting permission is more than just knowing how to write a sentence.