When people are removing paint from brick, they often consider highly abrasive methods such as sandblasting or power washing. There is no doubt that power washing will remove paint from the surface of brick, but it will also cause serious damage to the brick. The extent of the damage depends on how old the brick is and how strong the mortar is that is holding the bricks together.
Bricks and mortar are very porous. Water blasting at the surface of a brick will get into those pores and start destroying the brick from the inside. It can also weaken the mortar which will cause damage that one would not see until the wall collapses.