Someone attacked one of my planets and set off one of its traps, I went to attack said person and a halcyon went off. If I'm not mistaken attacking a planet is an aggressive action so the halcyon should be nulled the second he hits that attack button. Is this a glitch or a flaw Dan hasn't addressed yet?

I believe this falls under "failed aggressive actions". In so much as a person can trigger all your traps, and so long as they don't disable you or actually attempt to invade the planet they don't count.

he might have activated the halcyon trap after the attack?? (I don't use halcyons and I havn't invaded a planet yet)

Just attacking doesn't remove it, they have to invade. Thing is, that might be pretty handy for you, because if they're attacking and you set of their Halcyon they can't keep attacking, planet saved!

This guy has been attacking my planet for over a week now and now he's hiding behind halc so I'm pretty fed up at this point and the fact that the halc works just takes the cake.

He's doing it because he wants you to flux it more than likely. Nobody attacks a planet that many times just for giggles, and hes clearly not trying to take the planet, so he wants you to flux it.

Are you online and hitting him when he attacks, or are you attacking him later?

If someone wants you to flux a planet, they will continue to attack until you flux it, its very common practice to do this especially on better planets **xMR planets that you dont feel like purging, maybe contact the player involved and pay him to purge it 50-100ctp usually does the trick

I stole it about 3 months ago from him and he doesn't seem to get the fact that he's not getting it back and I'm certainly not going to pay him to purge it.

make him burn his halcs... halc aura drops after 2 hrs (sooner if he hacks or raids someone), set a timer and get back to him later

I taunted him, master troll in disguise. Have my alert now but would still like to hear from dan about this.