Some times when a coral gets into a scuffle it is not via sweeper tentacles or chemical toxins, some times it is simply a matter of collision and when this happens the winner tends to be the faster growing of the two species. There are some obvious exceptions to this rule as some corals still have their mesantenal filimants and others have developed a growth method that allows them to cover or shade their neighbors
Notice the burnt tip on this branching monti.
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Here is a green montipora capricornus growing into an adjacent red montipora digitata. as you can see the cap, with its faster growth and plating skeletal structure, is going to win over the digitatas encrusting and slower growing nature.
I will keep my eyes peeled and camera ready for more of these incidents as I have seen many but have documented few. It would be nice to have some photographed instances of corals running rampant.