Depending on your needs/budget it's probably not a bad way to go... if you have a large-ish open-source project and want to localize to a few languages, an initial pass like this, while taking pull requests is probably the best way to go.

Yes, the best way to get the correct solution to your problem is to post wrong solution on the Internet and wait for people to explain why you're utterly wrong.

If you didn't do QA, can you really be sure the results were amazing?

if your standard is not "quality", then you don't need to do quality assurance. ;-)