I've done this type of cycle (the one I described in my previous post) I think 20+ times in the last 10 or so years, and I've yet to run into any thyroid complications.
I might just be genetically lucky to be born with a thyroid that bounces back quickly after T3 use, I'm not sure.
I'm guessing that people who struggle with fat-gain rebound post T3 use, haven't adjusted diet and training to suit the post-T3 rebound.
Since your metabolism will be in a slower state for the first month or so post-T3, you might as well Increase training intensity and cardio duration, since you will be less catabolic.
Not only that but you'd want to drop total calories a bit.
One thing I know people screw up on, is they purposely go very low calorie while on their T3 cycle, then when they come off, there is no where for them to go but up. Don't make this mistake, you want to be able to drop 500 or so calories off your diet post-T3 use, without starving yourself.
Plan it all out beforehand, and you won't have problems. This basic idea goes not only for T3, but steroids too. Hell, anything bodybuilding related.