What I expected to happen was...:

I expected that when I right-clicked the piece of armor I was holding would swap for the one I was wearing

What actually happened was...:
I wore the piece of armor I was holding while the one I was wearing disappeared

Steps to Reproduce:
1. Wear any piece of armor (e.g. a diamond chestplate)
2. Take another piece of armor of the same type (e.g. a iron chestplate or an Elytra)
3. Select it and right-click

The piece of armor you were wearing will disappear