Oomis, about the dikduk — you are right. Just most people talk that way, so sometimes I do also.
As to the matter at hand, what do you mean when was the last time I saw that? If it is a mixed sitting wedding that could happen.
As far as staring goes, it does not have to be intentional to make the wrong effect. I do not intentionally stare at women, yet sitting next to or across the table from dressed-to-kill women would have negative consequences for me. It would still hold true if they were to sit at a next table or couple of tables away.
If all women showed up dressed “no frills, no sheitels (snoods, instead)”, there would be less reason for separate sitting. even then, it still would be a ma’alah.