I've cut down this article to something less silly and aggressive. Essentially none of the misguided, high handed language on display in the previous version was being enforced against the unpaid amateurs translating on this site, nor should it be.
The short version is: that guide is essentially appropriate in the context of paid, professional, native English speakers translating for an audience of regular people. Almost none of which is true for this site.
Here's some of the things I find are off base and removed:
"In particular, if you can, don't make your translation any more specific than the original."
...no. English is a more specific language than Japanese. This is especially silly when taken with the next suggestion:
"But within the above, make sure your English is idiomatic and well-written."
Impossible for ESL contributors and extra-weird in combination with the idea of preserving Japanese style ambiguity. Moreover, it is simply not worth the effort. Most translations on the site are quick and dirty efforts aimed at understanding fan works, not enduring contributions to the literary universe. So spare me the high standards.
"Translations should be fully English if possible."
Does anyone pay attention to this? No. Thankfully. A knowledge of weird Japanesisms (like terminating a sentence with ~) is sort of necessary to understand a lot of the material on this site. This guide feels like it was written for normalfags. Know your audience.
"Make sure you completely understand what they're saying."
"Don't translate things if you can't quite grasp the last panel and/or the punchline."
I've done my best to follow these two, but they are mutually exclusive. Oftentimes you reach a point in the dialog where the difficulty spikes. Should you leave the entire thing untranslated? Yes, according the guide.
Does anyone do this? No. Should they? No.
Leaving things untranslated is a cornerstone of the site. Yes JPN is contextual, but it isn't black magic. It is completely possible to understand things in isolation, especially if they precede what is not understood.
Ultimately my problem with this guide is a misapprehension of the stakes. My opinion is: it's not that big a deal. It's just a bunch of fan art, and the people translating it are a bunch of amateurs doing it for free. If there is a bad translation on some downmarket oekaki, nobody cares. If this guide were followed by anyone (it isn't), translation efforts on the site would halt.
Because the site is a wiki, how a person translates and what standards they use to do so are specific to them. If someone is translating a popular work badly, they get corrected. The purpose of a guide is to provide guidance, not to scare the shit out of people.