Why do we get negative xp on losing some challenges?

Question

sometimes when I lose a challenge, my xp is reduced by a very significant number which is way greater than the challenge xp.

Answer 1

Losing a challenge always gives you negative XP. In your first challenges in a programming language, you will get some bonus XP for answers. They add with negative XP and may result in gain of XP even when you lost the challenge. And, loss XP = 32 - win XP. So, if you see 5 XP on a challenge, winning gives 5 XP but losing gives -27 XP.

Answer 2

You may not loose XP in all challenges. It actually depends on the XP you and your opponent have in that weapon and also, depends on number of challenges you've played in that weapon.
An instance is this:
You challenged me in Javascript,
I have 1800XP in Javascript,
You have 300XP in Javascript,
if you win, you may get up to 32XP removed from mine plus answers bonus,
if I win I'll get just 1XP because I might have mastered all the questions and no answer bonus may be awarded.

Answer 3

I think this happened with you just now
challenge declined!!!!