There are two types of marriages to think about...
The standard marriage where somebody is in the country of their intended and wants to get married. These types of marriages usually envision settlement and hence have an immigration angle. It could be to get married in the EEA and settle in the EEA, or to get married in the EEA and settle in the other person's country. Regardless, I have it in mind that the various marriage regulations in the EEA are pretty straight-forward and would NOT by themselves be the occasion for a question. Instead it's the immigration aspect that gets complex and drives the need to ask some questions. The common thread for those questions you've cited are that someone's immigration status is imperilled and marriage is the way to 'fix' it. Accordingly, this type of marriage question belongs to Expats.
The other type is a 'destinational marriage'. This is where the couple want to get married at some thematically charged location like the Hohensalzburg Castle or Reichenbach Falls or the banks of Lake Como or wherever. They may or may not want to settle in the EEA, but the driving factor behind their question is not a perilous immigration status. These questions belong to us.