You do not lose FP rating if you abandon, only if you time out. Unless you are really new 15% takes a whole lot of time outs. 150 battles if you have 1000 fights. You can abandon move on and be all right but it sux if you time out when you lose at that point some people put you on blacklist and you wont be able to go against them again.
Abandoning a match is fine and doesn't result in a negative score to your Fair Play.
Timing-out is not fine if it's a continuous tactic.
15% time-outs must be the result of poor sportsmanship unless you have the absolute worst internet connection on the planet. If the latter then you're going to have a very hard time getting anywhere in the game; if the former you really should play fair or many people are not going to want to interact with you