At these levels it's not such a concern about getting stuck with a bad job. You just don't use that developer again and the $200 didn't wipe out your company.

I've commissioned jobs like that on freelancer sites for a lot more and pretty much did the same thing. Paid someone else to rework it or reworked it myself. I wouldn't use them again, but I did still get enough of what I needed and the job got done.

I guess it goes the other way too. Let's say I'm uncommonly generous and most other consumers will be much more demanding and try to get away with whatever they can. So the same thing as a provider. You get burned by one buyer for $200, you just don't service them any more but otherwise don't worry about the chance too much.

you can look at Remotion's 17 completed bounties, where specs & acceptance criteria are always included: https://github.com/remotion-dev/remotion/issues?q=label%3A%2...

that being said, we have only had a handful of projects using OSS bounties so far so we haven't seen everything under the sun. I acknowledge what you mean by blurry lines and how/when they might occur. but as I said before, when specs/scope/acceptance-criteria are in place, it's really hard to go wrong