If you're a Hangouts user, you're probably aware Google is splitting its service into two separate ones: Meet and Chat. Although the consumer transition (i.e. for non-G Suite users) won't happen before the end of this year, it's fair to expect Google wouldn't add new features to the classic Hangouts experience and focus on Meet and Chat instead. However, the company just surprised us by adding the ability to report users into its soon-to-die service.
Although this is a minor addition, it's a useful one that wasn't available until now. Indeed, you could block spammy users, but there was no option to report negative behavior to Google. This is now fixed, as you're provided with an option to report the user to Google while trying to block them.
Doing so will send a copy of the last ten messages to Google for review, which will help support teams assess the depth of the situation.
The feature is only available on the web for now, and it's not clear whether it'll make its way to the mobile app, which is about to be phased out.