If a player has just spent money in order to respec his traits, please give him a way to undo changes he acidentally made and didn’t want (missclick or sth. like that). If you happen to click the plus sign next to the trait line just one single time too often, there is no other way to undo this than having to pay again. Why is that? It’s very annoying.
Since I see hardly any use in this mechanic than having an additional gold sink, and annoiyng players that missclick during trait point distribution, I suggest you add the following mechanic: Whenever a player has spent a trait point into one of their trait lines and after that, closes the hero panel, a message appears that asks them to confirm that this is the trait point distribution they wanted. Until the player confirmes, there is a “Undo changes” button on the traits panel.