The "scary underscore" expression isn't scary because it's an underscore, it's because it implies the evaluation of JS, such that you could (and obviously wouldn't) do things like

    v-for="x in console.log('hello world!') && fetch('/') && [1,2]"

(my syntax might be off since I don't use Vue, but the merit should still apply)

My point is that when your templating language starts doing things like this (and inevitably, all of them do) - you've created a new programming language that is generally less thought out as one than deliberately made programming languages. Although the above for loop is evaluating JS, the syntax is decidedly not JS.