I bring this up because it was obvious that Katarina knew that Minako was Sailor V and therefore she knew she was Sailor Venus. Along with Venus, Mercury's identity was known by Ryo which brings up the question, what other characters in the show do you think know the identities of the Sailor guardians?
Yep. Naru (Molly) definitely knows Usagi (Serena) is Sailor Moon (Sailor Moon R Ep. 87)
And I think Rei's Grandpa should have a glimpse that Rei is Sailor Mars. So many to recall
but I think Naru is probably the most obvious one of them all