DG, I'm think voice and sight can set them off. Seeing as the LBS in their mind is the reason they think they're unhappy. We're not though, and this is why we go dark. Having as little contact as possible with the MLCer in this phase prevents us from being the target. It's a protection for us. If we have to have an interaction with them this is why it is so important for the LBS to act 'as if' they are happy, and capable. It relieves that guilt from them about us taking us out of the line of fire.
Make no mistake though, that anger is still there. MLCers don't recognize that happiness comes from within and they don't realize their anger is coming from the same place.
MLCers don't seem to have control over much in their lives, and that anger boils over like a volcano and wipes out everything in its path. Step out of the way and let it flow around you. OW is in its path now and better her than you at this point. Yes, things seem rosy in the beginning, but the anger has to be directed somewhere. In time, especially if you've made yourself scarce, avoided R talks, avoided pushing their buttons, avoided reacting badly when they've tried to push yours, guess where the anger is going? Gee, wonder if ow thinks she has such a prize now?
Take the high road whenever possible DG. Do not give your H and ow anything to bond over and form that triangle with its point directed at you. In time they'll be aiming at each other.
A person can't miss what has always there and provoking them. Stay as dark as you can right now. In time, just as your H is thinking and rewriting your marital history to make it all bad right now, the sitch between he and ow will eventually start to unravel. That's the time the good things about your marriage come to the surface for them again.
The way I see it is the fewer recent bad memories you've created about you for them during this, the less they have to wade through to remember the good things.
This all takes so much time to be worked through and processed. Time is on your side though as it gives you a chance to work on yourself and resolve your issues. When/if you get the choice to reconcile your M the less garbage an individual brings to the table the less to get in the way of the truly hardest work of all, piecing.
We all have setbacks just learn from them and keep moving forward.
