I see no problem using bleach on corals. The very nature of a coral's bicarbonate skeleton is a flow-through design, whereas wood is designed for water/liquid retention (and that is my main concern). It is certainly your prerogative, if you've had no problems, then feel free to keep with it. My choice is to not take the risk, and I will advocate this to others. Also, I am sure you use a very diluted mixture and it may very well be perfectly safe, but heat sterilisation is as effective and there is no addition of any chemical (which eases my mind).
An autoclave is a strong, pressurized, steam-heated vessel, used in our laboratories to sterilise instruments, pipette tips, etc.....