There are some people on the forums of whom are vulnerable and susceptible to emotional distress from the discussion of particular topics - known as a "trigger" because it can "trigger" negative emotions, intrusive thoughts and so on.

The point of this is so that users can hide a certain part (or all) of a new thread or reply to a thread if they believe it may be a potential trigger/triggering content. We already have the trigger icon, but this is useful if you only want to highlight a certain except of the text as "triggering". When used, the triggering content will be hidden and can be displayed by a reader by them clicking "Show".

You can see an in-depth post about the point of it here: http://forums.psychcentral.com/4311402-post119.html

Please give this a read for more info: http://forums.psychcentral.com/4311402-post119.html