Fingernails are not subject to the Rule of As-Is, my new term for the aspects of appearance someone has as a mortal that will be strictly adhered to when they are turned (like the fact that they are missing a limb, or their hair is shoulder-length, things like that).

[X Lestat left one of his vicious little thumb rings w/ me <3]

It could stay uneven/broken for other vampires in other media.

Why aren’t Ricean vampire fingernails subject to the Rule of As-Is? Well, as you say, an uneven/broken nail would be hella inconvenient for eternity! But none of AR’s vampires ever mentioned having this issue, and with so many vampires, who have known so many more vampires, collectively, surely one of them would have brought it up by now if it were a thing. So I have to conclude that fingernails are not subject to the Rule of As-Is.

[^Claudia’s aren’t long but she was a child, special exception. In Ricean vampires, their nails also have a kind of glassy sheen also my hands are prettier than Louis’ hands]

I headcanon that their nails grow to a certain length when they are turned, longer than they were in life, and will grow back to that length after being filed down. Lestat files his nails, he’s doing it in IWTV:

“And he drew
from his pocket a nail file, and, seating himself on the foot of the old
man’s bed, he began to file his long nails…  I could
hear the old man talking to Lestat; Lestat, who sat with his legs crossed,
filing and filing, one eyebrow arched, his attention on his perfect nails.”

Bc in vampire lore, in general, abnormally long fingernails are considered a sign of being a vampire. This comes from the fact that when you exhume a body from its coffin (to check to see whether dead Auntie Vivienne has been turned into a vampire *gasp*), the nails appear to have continued to grow, therefore, Auntie Viv must be undead! In fact:

“It is not that the fingernails are growing, but that the skin around them retracts as it becomes dehydrated, making them appear longer. When preparing a body, funeral directors will sometimes moisturise the fingertips to counteract this.” [X]