I vote for displaying the ID.
It serves as a ristrant for trolls.
It also keeps track of comments posted by the same person which ensures their reliability.

If any meyhem is caused to any thread by revealing the ID,
it is the result of back-stabbing and mischievous behavior.
Obviously not worth the sympathy.

Even in that case, things will settle on its own eventually after a while, anyway.
I just can not see the reason why to go against it.