The only thing I won't talk about is woman who were in my life. And I never ask about men that were in hers. If I or she choses to talk about that then fine but other then that I feel it non of her business and none of mine either

Other then that I leave nothing out.

Most people know what is going to matter to others. I think it is lying if you let someone believe something you know is not true even it it doesn't commonly matter is still lying.

Example
Most people do not care about resolved health issues.

But a Father of four kids who has already endured a slow agonizing death of one spouse to cancer probably wants/deserves to know if you had a radical hysterectomy in your twenties and there is a pervasive family history of cancer.
Anf that means going in before he and his kids are attached to you. It's fine if everyone wants to take a chance but it is a collosal deception and betrayal to keep that informatipn off the table.

This is an excellent point, and illustrates better than I did, why I am wary of using the label "betrayal" too readily. Because there are so many times when what is important, is entirely relative.

We can't write EVERYTHING into our profiles that MIGHT set someone else off. It's just impractical.

Not to mention, a specific irony about the question itself: someone who is primed by their prior experiences to THINK that you are "betraying them" by any and all omissions, likely has a kind of emotional baggage of their own, which would qualify as a "betrayal" of you, on THEIR part.

That's why I'll stick with limiting "betrayals" to those instances where the person actively and purposely hides something that they are CERTAIN would be a problem to you. Without the intent, there can be no betrayal.

I agree that "intent" is critical. And at time's circumstances make people hypersensitive" to see something ad a betrayal when no intent existed. All scenarios can not be covered or anticipated.
Profiles are always only a starting place regardless of length.

I do think it is helpful to have a list of questions that are important to you to cover over time but someone who does the drill and grill approach to on line get acquainted makes me run in the other direction as too wounded to ever have a healthy relationship.