Minimap changes in Eliminator?

In Eliminator, the minimap has some new features... does anyone know the explanation for why sometimes player dots will flash as a star? There are several types of stars. How does this effect gameplay? My best guess is that it has something to do with the players current skill chain, but I don't understand why other Eliminator players would care..?

Also the size of the player dots seems to change? sometimes a dot is bigger... why?

Lastly, has anyone else had difficulty challenging a player even though they are eligible for a race? I feel like about 30% of the time the horn does nothing, even though the player is not currently changing cars or racing other players.... maybe this is just a bug?