I must admit I have been guilty of doing this in the past. Rather than something negative though it was something positive. I think by telling it over and over it was a way to relive the experience or just express how great it was since I had no one with me at the time. In my case though I genuinely just forgot I told the people the story since I was telling it to everyone and (to me) it was an interesting story. Everyone was polite and didn't remind me that I have already told them the story until one person couldn't bear hearing it another time. It was only at this point that I became conscious of what I was doing.

I know what you mean though. Mentally ill people have a habit of doing this. If you listen in on one talking to themselves you will hear a story of some personal trauma they experienced some time ago.

Perennial victims also do this as a solicitation for love. While as a child we learn to express our bad experiences to our parents and receive love and affection in return. The problem is like drug addicts some people grow up to abuse this to lesser and lesser effect.

When it comes to aggrandizing it can be funny to shut the person down by expressing your disinterest then immediately complimenting them on something trivial that you genuinely like or asking them the question about something you wish to know.

Your comment reminds me of the phrase "People don't do things to you they do things in front of you." It expresses just how performative human behaviour can be at times.