Collusion — signs and what to report?

[dreamer13]

In any case, it's very difficult to enforce soft play rules. Even in a casino, you'll have regulars or friends/family members who will check or light bet/fold to each other more often, and as a dealer, you often can't tell whether they're simply playing their hand/stack/common strategy or playing soft. Warning and observation are all you can do, unless it's blatant collusion.

 

[Fosterbio]

I suspected that two players were matching online, as they were checking after making other players fold. What are the typical signs and whether it is possible to report them to the site?

Perhaps they were both deep stacked, unlike the other players. And they didn't want to build up the pot specifically against each other... But you can and should always contact security when you see a trick. I don't like team players or any other scammers.