Punctuating for emphasis

Hmm, good question.

I think with the example you gave, the words can both be capitalized like one-word sentences, as they're real words. The trouble happens with a syllable breakdown (not an official term; I'm just trying to explain what I'm seeing) where not everything is a full word. E.g. Non. Committal.

It seems to behave a little like an infix, where a word is interrupted by another word, usually a swear or a PG equivalent, e.g. unbe-*******-lievable. For an infix, I would suggest either hyphens like I used, or maybe smashing it all together, e.g. unbefuckinglievable. But I think the hyphens make it easier to read.

But I don't think there's a hard and fast rule for infixes, which are exactly what they sound like: the equivalent of a prefix or a suffix, but thrown in the middle of a word.

About the only "rule" there is for infixes is they seem to go after 1 or 2 syllables and (maybe) before at least 2 syllables. But this is a rough "rule".

The reason why I am tangenting into infixes is because they serve a similar purpose-- to add emphasis in the middle of a word.

I suspect that there's no actual name for this yet. Technically, it's not even Interrupted dialogue, which would be handled with an emdash, then closing quotation marks, line break, and then the interruption--- because in this instance, the interruption isn't coming from anyone or anything external to the speaker. The speaker is deliberately creating the interruption.

I suppose this is a very long and roundabout way of saying that I have no idea. But if I was tasked with creating a rule for this and naming it, then this is the sort of logic I would use.

Un. Helpful. -- I know.

I thought sticking a word inside another was called tmesis.

Oh, how interesting. I hadn't heard that term. My linguist boss several years ago used the term infix. But I suspect they're a shade different from each other. Hmm checking the internet, it looks like an infix only (maybe) refers to expletives.

Fascinating stuff and thank you for teaching me a new word.

I learnt it today as well.

THANK YOU.
I never got an email to tell me this post got replies, so I'm glad I checked in of my own volition again!
So, I had looked into tmesis, didn't hear about infixes until just now (though I was aware of the concept, of course), and even nobody's come to a concrete answer, I'm feeling more relaxed about it now and I thank everyone for contributing their knowledge.
It's almost exciting that there's no rule to ascribe to, in this case.
It all comes back to "What will be clearest for a reader to understand," I suppose. So although a period and a hyphen and a comma all have a different rhythm in my mind - perhaps they do for everyone - I'll just have to ponder what kind of cadence I'm going for and use my best discretion. Think I'll go with ellipses in this particular case!
Thank you again for helping me think through this. Y'all are the best.
Awe... some. :]

There is a bloke on YouTube who talks about this. There are rules we all follow without realising it. For example we would say "Fan flipping tastic." Not, "Fantas flipping tic."