It really depends on what armour you’re wearing. If it’s knee and shin it might get in your way, but if only shin you should be fine. Besides you will soon learn to learn new tricks around the armour.
About getting rid of scars… I don’t know. Some of mine have gone away with time, but others are here to stay. The best way to prevent a bite from scaring is to bandage it really well right away and keep it moist throughout the healing process. In other words don’t let it scab. And always wear the armour. THe other day I went out to ride (my bike) and had a debate in my mind whether or not to wear the guards and i was like “nah, I’m only gonna be out for a few minutes.” And then bam a pedal bite cut almost to the bone.
Take a look at this http://www.unicyclist.com/forums/showthread.php?t=78216 YUMMY!