I really think it's not an OK choice. A config file format that doesn't allow comments provides some of the worst possible UX.
One of the nice things about config files is that normally they are self-documenting, explaining the meaning of the various directives and providing possible values.
Without comments, you have to constantly switch between the documentation and the config file.
Also, the restriction on trailing commas is another really bad issue for a config file language as it pollutes diffs, makes moving lines around needlessly difficult and is one more landmine waiting to happen for the sysadmin editing a file.
No. JSON not at all OK as a config file language.