a bad fuel filter probably means it is getting clogged up. that means it will start to restrict fuel flow going to the injectors so you will start to notice loss of power and will put a strain on your fuel pump which may fail if not replace.
The system in a diesel operates at a high pressure and a dirty filter could cause several problem. Most noticeably being a lack of acceleration or poor running.
the fuel filter is must for every bike, for bad fuel filter can not filter the fuel, that if dust is there in fuel the bad filter can not filter the and can not give cleaned fuel to bike