Suggested dialogue [change]
For example, in "Can't you do anything right?", the words are not intended to start an investigation or to invite any response at all. What the words actually mean could change according to circumstance. It could be a little joke between friends, or it could be an insulting criticism. Generally, it would be taken to mean "You can't seem to do anything right".
The role of context is always important if someone asks "What does that mean". Consider this question: "Do you think this treatment is just?". There is no way of knowing whether this is a genuine question or not, because we do not know what the circumstances are. This is true of many kinds of communication, that what they mean varies according to circumstance.
On the other hand, "Is it right for a murderer to be allowed out of prison after only ten years?" clearly asks for the reply "No!". This is because the questioner has signalled what answer is expected.