I really do seem to have a talent for finding my way straight to use cases that libraries really weren't intended for; in this case I'm trying to use #handlebarsjs with custom helpers to implement my own simple/lightweight #nepenthe document format, and that gets me about 90% of the way there, but the way I'm using custom helpers and partials, I'm realizing there no way to access the root context without explicitly passing it to my under-the-hood helpers and/or partials in the source document.
Which makes sense when considering handlebars from the perspective of a developer tool where you're going to dial in your templates and forget about them... but doesn't make sense when trying to provide a simple document format for myself and others.
I think I've got a workaround though.
$dayjob has been slow, so I've been hacking on my #webmention fetching code for monkinetic.blog. Now using #handlebarsjs to render webmentions, and it's mostly working.
I'm now working on just styling it - adding author photos, making the comment html render correctly, and support activity types (cause Ryan Sharp sent a "like" and that's awesome https://snarfed.org/2017-12-20_diso-after-10-years-monkinetic-blog)