Disallow not vertical rhythmed line-height.
Sources:
The following pattern are considered violations:
.foo {
line-height: 12px;
}
.foo {
line-height: 1.3;
}
.foo {
line-height: 50px;
}
The following patterns are not considered violations:
.foo {
line-height: 24px;
}
.foo {
line-height: 1.6;
}
.foo {
line-height: 48px;
}