Etiquette for declining a wedding invite

I understand why you’re hurt, but I would stop trying to guess how they felt about the invitation as you know you had your reasons for inviting certain people to the day and others to the evening. How they feel about it isn’t your concern and if they were upset, they should have reached out to you (not another friend instead).

I wonder if some of these friends are people who haven’t been married/been invited to many weddings, and therefore just don’t understand the organisation, the etiquette or the kind of decisions you’re having to make.

If you’re wanting more info from them, you could send a message telling them you’re sad to see they won’t be coming as you’d really been looking forward to having a dance with them etc., and see if they respond.

I wouldn't overthink it.

Many people are quite formal in how they respond to a wedding invitation because, traditionally, it has always been a formal invitation. So the guests who are declining may not have realised that you would appreciate a more chatty response.

If they are miffed, that's their problem, not yours.