The user goes on to explain how the issue occurred, by stating that they think it was due to the Immersive Amazing Follower Tweaks SE mod.
For those who are unaware, the Immersive Amazing Follower Tweaks is a tweaker version of the original Amazing Follower Tweaks mod which adds new functionality and makes changes to the dialogue menu system.
Likewise, if you want to recreate this bug, you should ensure that Lydia has clothes in her inventory while the wedding takes place.
Skyrim bugs are often the most exciting to see, and one of the users has shared one that gets Lydia undressed in the middle of the wedding.