This is really odd. Harry has every right to talk about and reference his dead mother. Why would it upset William? He hasn't forgotten she's dead? No one dead can comment back, should we just forget all the dead people? If Harry (and William) want to talk and reference their mum then they should. If William chooses not to because that's how he deals with things that is also fine. I can criticise Harry for a lot of things but missing his mum isn't one of them.
With all respect, it is different to talk about a dead family member privately with family and friends.
But Princess Diana was (and is) a public figure and Harry held these speeches referencing her to large crowds, knowing that they would be transmitted via global media outlets.
The way he does it seems to me (!) as if he wanted to benefit from the relation. He is grown-up and should maintain a public profile on his own merits, if he so wishes to do so.
But then again - he is critical of media and feels haunted by them and he feels that the media killed his mother.
But why then discuss her in front the media, very publicly?
Why does Harry himself not grant her the privacy that he felt the media should have granted her?
To me, this is a contradiction.
And yes, I also think that he should be considerate of Prince William, as Prince William is still part of the BRF and will (according to current information) be King one day and Harry's remarks about their mother will also rub off on William.