In speech, at least where I live, it is possible to change intonation so that a sentence is understood as a question or that it's understood as a rhetorical question. There is a difference in intonation.
Question has an accent on the end:
. . . X
Rhetorical question has an accent before the end:
. . X .
Usually, rhetorical questions can be preceded with words like, maybe, possibly, probably, etc.
Assuming that the basic role of writing is to emulate the speech, rhetorical questions can be represented both with and without a question mark.
Not using a question mark in a written (non-rhetorical) question is rather confusing in that sense.
The usage of punctuation and various other forms depends on the author and on his/her ability to express, as does the burden of understanding rest on the reader.
Sarcasm and irony in speech are used rather freely, sometimes the author wants their message to be interpreted certain way and sometimes they just want to disguise it. The same can happen in writing.
There are also cases of misinterpretation and misunderstanding, which are rather common in the realm of communication between two entities using different sets of associations/meanings.
The kind of proposed change wouldn't reduce the amount of misunderstanding. It is possible to teach children a protocol of communication and it's called formal communication. Most of these problems happen in the informal communication and then it may be possible that miscommunication is the intended element of the informal message.