The second point was actually brought up here [Bug] Forced autocomplete commands aren't very user friendly as part of a bug report, but it’s nice to have it be formalized as a feature request too.
As someone with a rather unique name, I can’t say the first has happened to me too often… But I can understand the concern. Requiring a last name when multiple characters matching a given first name for a command would be useful. If there are two Adams in a room, require their last names for whispers, messages, etc. Just two online, but only one in the room, whisper doesn’t need it but message does. etc. etc.