Hi o0 IZZI 0o,
Glad you were able to get the name changed.

I'm not sure what the issue was, but it could have been that your display name change took a bit of time to update on Jagex's lite highscores (their raw data source, not the visual highscores). But it seems to be all good now.
As for how usernames display - unfortunately the Jagex highscores do not provide information on a name's capitalization, so knowing how a name is really supposed to appear in terms of capitalization is difficult. There may be a way to do it via the Adventure's Log, which I'll have to look into though.