Both, because there are so many different situations that can cause a double we give negative two points to both fencers, its a little harsh but makes people more conscious of their moves
Yes, for example we hold small club wide competitions, these point contribute to a final score, it also is a great way to even the playing field between experienced fencers and new fencers, new fencers double less because they are more timid and methodical, where experienced fencers tend to be a bit more aggressive and focus on speed, we have had people end with negative points lol