You can tap the data stream, or try to find the information in RAM (depending on what info is sent back to the client) but that in itself might be banable (the memory part would just be a PITA) and that assumes they don't encrypt the stream.
Oh look someone hit the nail on the head.
Yes it really depends on how the client handles it's own memory and where the combat log information is coming from. Also, you don't really need to hit the combat text per se considering the game itself has methods to display other player damage to the client (via menu options).
I'm not going to get into how to handle issues like what you mentioned... for the reasons I stated earlier.