What are some general clues that indicate if someone is playing the role of saboteur? Obviously if player is going to put a troublesome dead end on the only path he's a saboteur. But some players are more subtle, and they come out of cover late in the game. How can I spot a saboteur early on in the game?
- Obviously, if you are a digger and someone is continuously destroying your tools, you might expect them to be a saboteur.
- A less obvious way is to detect who are diggers and use deduction. You know ahead how many saboteurs there can be in your game so if you can eliminate some players the chances for others to be saboteurs are getting higher.
- Look at who is an obvious digger, and look at who is destroying their tools, or blocking their paths. Obvious diggers are easily targeted by saboteurs, so that is another way to spot a saboteur.
- You could argue that in the end the best saboteurs are those that remain hidden for a long time, but this could also be a weakness, if you are a digger and you find it hard to detect whether a player is a digger or a saboteur, maybe they are playing hard to read because they have something to hide. Arguably diggers have no advantage having their identity hidden so a player who is hard to read is more likely to be a saboteur.
And if you still don't know, just call them a "saboteur" and see what the general reaction is. :-)
Another way not mentioned by @Bazzz is to keep an eye out for when people make rockfall spots. As a Saboteur, it's useful to place paths in a way which you can claim to be good for the diggers, but with the real reason being that with a correctly timed and placed rockfall, the gap is harder to fill. Call out people who create these spots and encourage actual diggers not to do this.
This is something new players often have trouble grasping.
This flowchart is how a computer AI would decide(from here), but is pretty useless to humans. I'm just putting it here because I thought it was kind of cool: