If "He does not demonstrate his age." is considered correct, shouldn't another valid reading be "He does not demonstrate her age."? We have not used 'proprio' here, so it could very well be that 'sua' refers to someone else.
In English, "He doesn't show his age" is ambiguous, and it's not the natural way to say either of the possible meanings. It's a peculiar way of saying he doesn't appear to be as old as he really is; the more natural way, for an American speaker at least, would be "He doesn't look his age." The other possible meaning is that he doesn't reveal his age, i.e. he won't tell you how old he is. In neither case would a native English speaker be likely to say "He doesn't show his age."
It's not peculiar at all. I heard an NFL announcer recently say this about an older player, and it seemed perfectly natural.
The possessive pronoun goes with the object. For "età" is feminine singular, it has to be "sua". "sue" is feminine plural.
It is not ungrammatical, but you probably wouldn't say that in English. You'd probably say "He doesn't look his age" or "he doesn't show his age."
Technically that's possible, but it's also ambiguous: it could mean that he doesn't look his age, or that he doesn't act his age.
'He does not act his age' was accepted as well, so I guess it means both to 'look' ones age as well as to 'act' ones age.
is this he doesn't show his age as in a 40 yr old man may look 30? Or is this used the way American's use "He doesn't act his age"?
why not use "mostra" here instead of "dimostra?" What's the difference and what is the context for using each?
Why wasn't "He doesn't show his age" accepted if "He does not show his age" is?