(I understand that "word" is not an especially rigorously defined concept, but I hope the question is still coherent.)
In the computer game series [空気]{くうき}[読]{よ}み, I noticed that the player's efforts may be rated as 「そこはかとなく読めてるっぽい」(localized: "very vaguely considerate").
Jisho gives a base form そこはかとない:
I-adjective (keiyoushi): 1. faint; slight; vague; nebulous; indeterminate; tinge of ...; touch of ...
I can't find any evidence of kanji being used to express this, even very rare ones. It doesn't make sense to me to have this many kanji-less kana in a row for a "single word". To contrast: I know that e.g. よろしくおねがいします is commonly written all in hiragana, but it also seems fine to write as よろしくお願いします; and [宜]{よろ}[敷]{し} and [御]{お} and [為]{し} at least exist - such that 宜敷く御願い為ます seems at least theoretically possible, if extremely chuuni. But for そこはかとない I can't find anything analogous1.
When I first saw this, I assumed the は was particle-wa, which naturally suggests a decomposition そこ + は (topic marker) + か (interrogative particle) + と (quotative) + ない. However, I can't make any sense of that grammar (in particular the は-か combination), and certainly can't relate it to the dictionary meaning.
Is it a set phrase consisting of multiple lexical items? Or is it some kind of lexicalized expression? In these cases, how can we parse it? Is some kind of elision involved?
Or is this just a word that has always just been a word, that somehow never involved any kanji, and suspiciously looks like it has all these other short words and particles in it?
1 Unless, of course, it does break down into pieces the way I imagine, in which case I guess [其処]{そこ} and [無]{な} would apply. Anyway, the point I am trying to make is that the existence of those kanji helps establish よろしく and お (prefix) and ねがい and します as separate lexical items.
