For awhile there were little lines drawn between Ash and the past cause there was very little mention of any prior accomplishments or ventures.
In Johto I think he may have been bragging to Casey at the beginning of the Saga when he went over kill on her with Charizard. Then Shingo in "Wired for Battle!" mentioned Ash was lucky to make the Top 16 in the Indigo League.
The reason he may have mentioned his accomplishments to Reggie is cause he may have been telling Ash all that Paul has went through as well which is pretty much the same places same as Reggie.
He may have, but at some point they will probably be brought up if not already.
And with their first meeting I think Trip was too busy being a jerk himself, which I remember mostly Trip insults toward Ash being from Kanto.