Agreed. A project maintainer's job is to accept comments and improvements from the community. It is completely irrelevant if someone is getting paid for their contributions, as long as the quality of their submissions are up to snuff.

If you think that people contributing to your project should not be compensated (which is a reasonable thing to think IMO), the burden is on you to make sure they are not, and it is not the responsibility of a third party to make sure that they are not getting paid.