Alright, after reading up all of the suggestions from the Question form (which sadly, are a bit dated, most many years ago), I am asking for your help.
Should be fairly easy, but not really quite catching it!
I created a custom screen for entering a comment when transitioning a task to Blocked status. I would like to add a text that Reads "Please state the reason why this task is blocked".
In the future I would like to make it all dandy looking with status options, but for the moment this will do.
However, I got to achieve only this:

Anyone can help me make it a little bit more descriptive? Maybe default text on the comment box, or a label? I'm looking around but not really finding my North.
Thanks a lot in advance!