Well you’re on Reddit for one, people confuse online with how real life works. To answer your question it depends from person to person what they think matters. I’d say comparison is the thief of joy so it’s in your best interest to not do that with a partners ex’s. For something like body count it depends on why you care about it . As an example if you care about it because you think a girls “run through” that’s not great. If you care because you value sex and intimacy a certain way and want a partner who shares that then I’d say that’s reasonable. We are human though and I think a good partner would give reassurance to genuine insecurities.