What is the universally accepted symbol for indicating a proper subset in LaTeX?

[Ben2]

The page on LaTeX includes two symbols for "is a subset of." The first (on the left) is used by some to mean "is a proper subset of." But that notation is not universal.
Those who commonly use the second symbol (on the right) to indicate "is a subset of", often indicate "is a proper subset of" using the same symbol with a diagonal slash through the horizontal line.
To me there needs to be some universally accepted symbol to unambiguously indicate "is a proper subset of."

 

[mfb]

This subforum is for suggestions about the forum, not suggestions about how mathematicians write something.

The version with the slash is unambiguous, and everyone will accept it if you use it: $\subsetneq$
You can't stop mathematicians from using other symbols if they want to.