A few months ago, someone in a programming class showed me a vim plugin he found that used Unicode to make source code "look pretty." I remember, specifically, that one of the things it did was make HTML comments (<!-- and -->) joined and look like one Unicode "thing." Note that this is just during rendering; the file itself still didn't have those Unicode chars.
An example of the sort of transformations it did would be how the code looks like on this demo page of a programming language that is not related to the question: https://blog.usejournal.com/introduction-to-clio-40dbbf9c250b
Specificlly: 
As you can see the -> is being rendered "as one character," as is the =>. (likely using conceal)
There is an Emacs plugin that does this, but I'm 80% sure I saw it was for vim.
I am aware of the implications and downsides to a plugin such as this, however, I would still like to know, what is this lost plugin? Where does it live, and how would I install it using plug?
