I really put this up to get others' opinion on this without the subject warranting a new thread but since yours is all I am getting then I will ask a legitimate question to you. Do you just go off without possibly the neighbor even knowing their property is in any jeopardy when in reality it is, esp the house one, in dire jeopardy....and forget it and sleep at night and not expect to feel any complicity when/if the house is squashed, people possibly hurt/killed...and you could have avoided that?
Its a sticky question. Does the ISA code of ethics address this specific issue? I have no problem telling the homeowner but the neighbor opens up a whole can of worms. I think you've done your due diligence in telling the homeowner, period. Its his tree and he has the ultimate responsibility.