I am currently working on a texture pack (hear me out) which makes armor see-through to appreciate skins more. I didn't want to make it fully invisible though because people using the pack would have disadvantages on servers.
Then however, I noticed that when the armor was enchanted, The Chestplate remained see-through, and the rest became solid. When removing the Chestplate, only the Leggings were see-through. When removing those the Boots. After that the helmet.
The pack changed nothing except for the opacity of the armor.
I know this could be seen as modified content, but it is a big restraint for texture pack makers, and I didn't know where else I could report this.
Thank you for your report!
We're actually already tracking this issue in MC-98308, so I resolved and linked this ticket as a duplicate.
If you would like to add a vote and any extra information to the main ticket it would be appreciated.
If you haven't already, you might like to make use of the search feature to see if the issue has already been mentioned.