I mostly use hickory, pecan, and mesquite and I've never made an effort to remove bark.
Never suffered from bitterness.
NB El Dorado Offset, Primo Oval Junior, Traeger Model 075 Pellet Pooper, Big Chief, Kingfisher Kooker 14" gas/wood combo, PBC Brethren Edition
Home Brewer, Murderer of Squirrels, Armadillo Inspector
Flaming Pig Head Mod
Black Thermapen, red backlit Thermapen
Certified KCBS BBQ Judge