she ... Said anything more than 'hi' was very wrong and it won't happen again.
Does that mean she admits to continuing contact with him? Talking about personal things, like races and vacations?
Also, "hi" is OK? I kind of understand this. They work on the same floor. They work in the same building. Everyone knows they worked very closely together. If he says, "Hi!!!" and she ignores it completely, tongues will wag.
Background:
7 months since d-day. There was a nearly 12 month long physical affair, after some lengthy emotional affair. Worked together for couple years on same project and landed in same office after and fireworks ensued. They work together on same floor to this day :-0
I must assume that they both are not professional actors, and even professional actors cannot be "in role" 24/7 - therefore, some other coworkers, probably many other coworkers, know that your wife and other man have been making "fireworks" with each other.
She is pretty transparent about activities outside of working hours since d-day. No 'signs' of cheating since d-day.
She is transparent outside working hours, she rarely tells you what is going on inside that building during working hours. I assume you wouldn't know if she had lunch with him at the same table in the company cafeteria. Which it seems that she does.
There was one admission of contact over Christmas, so almost 2 months after d-day. Nothing since. (I) Had a feeling at times, since that incident that 'no contact' wasn't being fully respected.
Your "feeling" that "no contact" wasn't being fully respected, I think that you have more than just a feeling about that now. I think you can see your wife knows all about other man's personal life.
Right from the get go it was stated there would be 'hi' – 'bye' interaction in lunch room etc. This is never mentioned when it happens.
Everyone knows your wife and other man are either (former) lovers or at least very close chums. I wonder if other man has found another paramour yet at work. Or if your wife is jealous of his interactions with other women, who he must also flirt with.
Do you work in an office? Do you understand the environment in a larger office like your wife's? The little flirting and romances, the personality "types" that populate any large workplace - the gossips, the flirts, etc.?
Consider this: Your wife sits down at the table in the cafeteria, puts her food all spread out, two other female coworkers sit down with her, and they are talking about the latest company news - "did you see the new employee in the accounting department who parked in the CFO's reserved parking spot?" Right in the middle of that, here comes other man, and plops right down with all of them, "HI ALL!!! How are you all today? You are looking very involved in some good juicy news, what is it? Mrs. 20yrsin, how are you? I didn't see you at the product development meeting, were you sick?"
I must assume that your wife will not pick up all her food and move to an empty table somewhere else in the cafeteria as a matter of social suicide and possible professional detriment to act oddly amongst coworkers, some of whom are superiors, some subordinates.
I really don't see how a reconciliation works when the two lovers see each other at work 8 hours a day, five days a week.