As pretty much everyone knows at this point, cheating on codeforces is becoming more and more rampant. I have 3 suggestions that will help both prevent and catch cheating.

Allow users to report cheaters

This is pretty self explanatory. I don't think there exists a report method, and it seems like the only way to bring attention to someone cheating is to make a blog post or comment which definitely isn't efficient.

Change cheaters handle color

Even if a cheater has been caught, they generally face minimal repercussions. It doesn't make sense to go through their account looking skipped submissions. Instead, changing their handle to a color that will stand out will deter them from cheating. If they are cheating to brag about their rating, all that will go away when their handle changes color.

IP Bans / Sign up with phone number etc

Also pretty self explanatory. The only problem I can see with this is that users that live in countries with restricted internet will have more limited access.