Just my own opinion and danbooru might have their own manual of style, but I'm not exactly agree with some of those reverse-spelling transliteration. It's just the way they're (used to be) written and it's perfectly normal. It would be like transliterating Arabic writing all reversed and such...Unless the RTL writing is relevant to the context I think it would be better to just transliterate it normally, and mirrored writing would be better using CSS transform.
Just my own opinion and danbooru might have their own manual of style, but I'm not exactly agree with some of those reverse-spelling transliteration. It's just the way they're (used to be) written and it's perfectly normal. It would be like transliterating Arabic writing all reversed and such...Unless the RTL writing is relevant to the context I think it would be better to just transliterate it normally, and mirrored writing would be better using CSS transform.
The thing is, it used to be written, and is odd even to the Japanese, to the point that people jokingly call Shimakaze "Zekamashi" even in Japan.
And yes, some translators use the CSS Transform to accomplish this, but not everyone knows how to use it or wants to go through the effort of using it, so you get translators who simply write it backwards.