Emotional affairs are difficult to pin down and describe, as essentially they sit somewhere between a close friendship and a crush. Usually in the work environment.
I would only class something as an emotional affair if there is genuinely no intention by either party to take things further, so no brushing against each other, touching, no meeting up behind partner's backs etc etc. It's not about flirting and drawing the other person in so that they leave their partner, it's when people genuinely have a connection with someone, but they're in a relationship and don't intend to end that relationship or to have an 'actual' affair. They would probably be together if they'd met single, but they didn't, and so they're not.
It is hard to accuse somebody of an emotional affair because often they genuinely don't intend to take it any further, and therefore they may argue that it's just a close friendship. They might have feelings for the other person but never intend to act on them, expecting them to pass.
At the end of the day, it's a very fine line to tread. At what point does friendship cross the line when nothing physical has taken place, there have been no secret dates or meet-ups, no socialising outside of the workplace (apart from the odd message)?
To me, if there's flirting and touching then that's not an emotional affair...that's the beginnings of something that is likely to turn into a physical affair (or have the participants end their relationships to be together properly).
To me, emotional affair is where both parties have feelings for each other but never intend to act on them in a 'real' way. They may imagine what life would be like with the other person, but they never genuinely consider ending their relationship to be with them.
As for your question OP, I think I agree that it's best not to know. The likelihood is that emotional affairs will pass in time, never having progressed any further, and your relationship would survive. In my experience, emotional affairs only manage to end relationships where a) it opens the person's eyes that their primary relationship is no longer working, or b) a partner finds messages or emails etc and is, understandably, heartbroken. It is very difficult to recover from, and some people can't.
I believe I'd prefer not to know as I would imagine that at some point in their lives most people form attachments to someone who's not their partner, and imagine what life could be if we were with them instead. That doesn't mean that we don't love our current partners or that we want to end the relationships we're in, or that the attachment won't pass.