Is there a way on here to report an issue or harassment to a moderator?

There is a report button in the bottom left corner of a comment

Probably try to reach them through Discord.

Normally if I want to bring something to their attention and it doesn't fall under the "report error / missing information" at the bottom of a page, the best thing I know how to do is:
1. Click the GamePress logo at the top-left of the screen
2. On the left-hand side menu you'll find an option that says "contact us"

I used it before the report flags were part of the Q&A section. They respond.