Yes, it certainly deters chicken bullies from pecking unassuming members of the flock. Must taste bad. When the pecked, bloody patches are covered in tar, the vulnerable chicken seems to relax a little, join the flock, step forward for food etc. Sadly have to re-apply after heavy rain but our bullied chicken is getting used to the routine. She never objects so the tar must feel quite soothing although it's a sticky business to apply. She can till flap her wings, poor sausage!
We are considering making their playground more adventurous and possibly introducing more chickens to see if this helps. We only have 4.
Tar is helpful but maybe need a better, longer term solution, beyond keeping her on her own.