If it's done well, then powder coating doesn't want to come off. Blasting it off creates a rough profile on the metal, Heating (using a burnoff oven) can warp the frame or melt it if its ALU. The best way is chemical stripping. Brake fluid or gasket remover should only soften the top but thats about it. The most effective stripper I've found so far is "Aircraft Stripper". It should cause it to lift but if not it'll soften the coating up enough to make blasting without damage possible. If you send it to a commercial stripping company it'll comeback stripped but I recomment a light blast to provide a slight profile to enhance adhesion of the new coat and an iron phosphate wash to prevent rusting before recoating.

A powder coat finish is NON porous. It's like a plastic film. Adhesion problems are common and are usually caused by poor surface preparation or not heating the part correctly. When the coating lifts off it may peel off in sheets. Adding an additional clear coat will make the coating thicker. If the coat becomes too thick it will chip easier.