You're assuming that all people think the same way.

People that think in sets, are very capable to understand commutativity so they can understand that a + b + c = c + a + b. Which can use "big sigma" notation.

The problem would be consistency. As this is a SQL Server 2014 forum, the old join syntax would not be available for outer joins. Even worse than using SQL-86 joins is to mix both standards just because you claim it's the way to think on a set based manner.