WW's post makes perfect sense to me..
It's about self esteem, or about someone who doesn't feel they deserve, or can handle a FT relationship.
Perhaps it's a problem with commitment, a fear that if she does, he'll reject her anyway, so she keeps one foot in, and then gets sucked in.
They create their secret and exciting bubble, their 'us vs. The world' dynamic. Naughty, but, erm naughty, 'i'm a little bit mad, me', i'm not as dull as you think I am, ooh, if only you knew what I was capable of..
And despite the self doubt, there might be someone prepared to fight the fight, against the odds, for me.
THEN i'll know that i'm loved, that i'm worth it.
A MM is, in a way, easier, cos he has everything to lose, so once the inappropriate comment's been made, and not rejected, he has to damage limit and go for it. Cos if he goes around chatting up everyone, sooner or later someone's going to say something.
He has ishoos of his own, he is defective for whatever reason. Again. Often inferiority rather than entitlement, he'll use the entitlement to defend his mistake.
Strong, self assured people don't cheat, don't abuse, don't lie.
OP, OW are kind of pathetic, as well you know. This is the time to choose NOT to be pathetic, to be strong enough to have some pride in yourself.
You are no longer an Other Woman, you are your Own Woman. Don't ever allow yourself to fall into that pit again.
Delete the numbers, block the cheat and get on with your proper life.