* I understand why you want to list A->B and B->A separately, but I'd say it should be the default that someone is able to translate both ways, so favour the common case and let users correct it later.
* Also, If I am fluent in N languages, I must list all the individual pairs, but it seems unlikely someone able to translate english to swedish and english to norwegian wont be able to do swedish to norwegian too. I'd say "list languages you can work with, then review pairs" is a better option.
What is there to guarantee the quality of the translation? I0've seen the stars, but they only make sense after a translator has worked for a long time. * Couldn't translators at least link/list previous works in the language pair? * Could we have some kind of meta-moderation? Say, each translator from lang x/y is randomly given a snippet of someone else's translation and can rate it. * Couldn't we have preventive moderation? Request translation of a tiny text for some non-profit org, say, two sentences of wikipedia, and submit it to other translators for validation (or just check it's not google translate's output)
I've seen abhorrent translations between niche languages (e.g. hungarian & italian) because the customer has no way to tell if the translation is good, and usually does not even have structure in place to _collect feedback about it_.
This means there is not even the chance of going back post facto to take back your money/improve your translation/give bad rating. In practice this translates into a perfect market for lemons
Finally: technical writing is not marketing writing, nor literature, nor drama and especially not legal speak, I believe listing categories in which you are confident is much needed.
But all in all, I wish you the best luck and these are mostly minor nitpicks :)