If "everyone does it", then you should treat it as clear and just part of writing the language idiomatically. Pick your battles for when even the cognoscenti favour the more verbose approach.

It doesn't help people not too familiar with the language.

It's perfectly clear and unambiguous. For some reason everyone loves it when functional languages are 'pithy' but hates it when C-like languages are equally terse.

How?

Smthg[i++] and smthg[++i] have two different behaviors. If you tell me that this is clear I probably don't want to read your code.

They're two different things. Are you going to complain that a/b and b/a give different results?

You're comparing mathematics term which have been established since before your grandfather was born with a peculiarity of the C language that confuse more people than it helps. People willing to Obtain a small amount of LOC for less clarity deserves neither.