This is probably it’s headline feature

Buttons will be added to the sidebar of any Lemmy or Kbin community you visit, which will let you open the same community on your home instance.

You can see the full description on the relevant store.

One of the custom icons is a tin of Heinz so I would assume so!

They are actually different (but similar) animals, from different continents.

That’s definitely not senior dev behaviour, was he also involved in defining the best practices? If so he should 100% be following them as an example to other devs, and if he has an issue with individual parts (which is fine) he should discuss with the team about changing them.

Aversion to tests is also a really concerning problem I would say. And you should not have to fix his code in PR, it’s his code!! I’m afraid I don’t have any answers for you but you are right to find this unusual!