/src/Standards/PSR12/Sniffs/Traits/UseDeclarationSniff.php ignores block comments.
For example this will cause the The first trait import statement must be declared on the first non-comment line after the class opening brace error to be shown:
class MyClass
{
/*
some comment
*/
use RegistersUsers;
while this will not:
class MyClass
{
use RegistersUsers;
/*
some comment
*/