I think it makes way more sense to put a conlang in Unicode than it does a peculiar stylistic flourish only ever applied once to a single letter in a single document. If that belongs in Unicode, why not every bit of marginalia ever doodled and every uniquely adorned drop cap / initial letter?

There is a smattering of missionary-made alphabets that have way less usage than some conlangs. Why are they legitimate but conlangs aren't?

so all you need is one crazy parent? shouldn't be too hard to find

https://www.dailymail.co.uk/news/article-1229808/Linguist-re... (2009):

“A linguist has revealed he talked only in Klingon to his son for the first three years of his life to find out if he could learn to speak the 'language'.

[…]

Now 13, Speers' son does not speak Klingon at all.”