Using modifiers alone
One common mistake I see often is around the use of the modifier classes. If you think a bit about what a modifier is I think it should be easy to understand my point here.
A modifier causes a modification, and a modification can only be applied to something that is already standard. Take the example bellow:
salad: tomato lettuce;
I'd argue that this is a accurate example of how BEM should work (at least leaving
elements aside for now). If we analyze the relationship between the blocks and its modifiers are, one can see that using only a modifier alone is nonsensical. Imagine someone in the kitchen receiving the
What does this mean to them? how will they make this burger, they will slap a cheese piece on the table and then remove it and deliver an empty tray with a napkin? Now, if we use it like it is supposed to be, modifiers in conjunction with the block (or element), now suddenly it is clear to the person in the kitchen that they are, firstly making a
burger, and secondly a
burger--no-cheese (with no cheese).
<div class="burger burger--no-cheese">
I guess the confusion comes from the naming convention forcing us to use the name of the parent block (or element) besides the name of the modifier, that kinda gives the impression that the modifier class can be something on it's own, but the real use of it is to change the behavior of an accompanying block (or element).
I hope that this analogy serves well to explain the relationship between a block (or an element) and its modifier, basically it does not make sense using the modifier alone, if you need to create a class for only one instance of a div, for example, I think that that is a good contender for an element class, not a modifier alone (or even a utility class, but some BEM purists are not really ready to that conversation yet).