'red-head scarf' certainly isn't an acceptable use of a hyphen, unless the scarf is woven from the hair of a red-haired person.

I read that as "A scarf that red haired people wear"

That would be a legitimate way to parse that phrase, but it's far more likely that this is a typo for "red head-scarf". There isn't a particular kind of scarf worn by red-heads, AFIAK.

Admittedly, I thought of the sexual double-entendre. Muff can make a nice scarf...

But I digress.

Motorhome is not hyphenated.

I blame spellcheck. In many cases the most legible solution is a German-style mashingwordstogether, but spellcheck systems highlight those so people hyphenate instead.

For example, spellcheck has a curly red underline right now. But would it really look better as spell-check?

Spell check, no hyphen. Easiest way to figure out what needs a hyphen IMO is to google it. Otherwise, just try to avoid hyphenated words, a simpler word will often do.

I think it would be more grammatically correct to call it "spell-check" or even "spell check" instead of "spellcheck".

Spelling check... you aren't checking spells.

At least, this is what I've been told by a very picky guy...