Brandir says thank you to Brandir for this useful post....

[wilomn]

It's supposed to be a way of saying 'thank you for that useful post' or 'I agree with you'. In addition there is a 'add to user reputation' button at the bottom of each post (I don't think this function shows up in tapatalk) where you can add a little note showing your appreciation. However with this function you can also add negative reputation which subtracts from the users reputation total. But only really mean people use it that way.

Indeed you can.