stringParams mode was originally implemented to support the legacy pre-Glimmer/HTMLbars view layer in Ember.js, but since moving to Glimmer, there's no longer any need to support stringParams mode, so we should probably remove it from Handlebars proper...

...unless somewhere out there another prominent library that extends Handlebars also makes use of stringParams? Does anything come to mind? Any good reason to keep it around? It certainly is a pain to maintain.