This question is probably dumb but I can't find anyone else on the internet who seems to be troubled by this.
The Legendre symbol is denoted as $\left(\dfrac37\right)$, which is very useful for number theory and quadratic residues. On the other hand, this very obviously looks like a fraction in parentheses. While fractions are not always necessarily in parentheses, I find this notation rather unsettling.
Is the identification of a Legenfraction in a context such as $5\left(\dfrac37\right)$ determined solely by the general context that it appears in? Is there an alternate notation (besides the plaintext (3 | 7)) that leaves no room for creeping doubts?
Parentheses around a single fraction are typographically unnecessary (see for example the comment about the use of \cdot ) - most probably influencing Legendre's choice, see extract below of the definition in his book $\underline{\text{ Essai sur la Théorie des Nombres}}$.
I do not find the notation confusing at all - but I admit I may be influenced by my habit of avoiding parentheses as much as possible.