TT, the shame and regret come so much later. I know it's hard to think of this as "early days", but this whole process takes so much longer than we can even imagine.
But as to others feeling regret, one female friend on RL who did this to her family in her 30s did tell me that she regrets it every day, even though she has remarried and is generally happy. Her H divorced her quite soon, and remarried so there was no chance of reconciliation, but she says that she was completely misguided, was chasing something that only happened in the movies, that it was too hard on the children, and so on. She also says that her current H would also still be with his original family if he had known then what he knows now, so it sounds like they were both MLCers at some point. (I don't know her new H's story).
Another RL acquaintance, another woman, also now has expressed regret... it's something like 8 years now, and I believe she started thinking this way around 3 years ago, but I'm not exactly sure of the timeline. Again, her H has a new partner and even a new child, so no chance there, either.
In both cases it took lots of time and lots of replay antics.
My H had some kind of episode of clarity around 2.5 years in, when he said that he was sorry he had treated me so badly for so long, but from what I can tell that was the guilt overwhelming him, rather than remorse. He chose to run further; had another smaller crash when he again talked about feeling so guilty, but again ran further.
I keep thinking about that line from one of RCR's articles where it says that they have to run until they can't any more.