The CSS allows that I can have a class called “.header”, as well as “.main”, “.footer”, “.aside” and so on... the same for IDs. In theory, I can have 3 selectors with almost the “same” name, like “article”, “.article” and “#article”. And I can do the same with all elements, including, why not, a class called “.html” and an ID called “#body”, etc.
For me, if I see the DOT I know that is a class, and if I see the HASH, I know that is an ID, so for me no confusions, but does it go against the naming conventions?