To my knowledge disabling the behavior for CamelCase node names is not possible – a case for a feature request. It seems, that at now you only have the option to write the word without CamelCase (= camelcase) and edit if afterwards or to remove the link afterwards.
ctrl-shift-r does indeed remove formatting, this has nothing to do with removing a link. The idea with a shortcut would be an alternative, if it would be possible to assign one to the command to remove a link. But this command does only appear in the context menu, not in the main menu and it seems, as if in the configuration window for shortcuts only those commands can get a shortcut, which are in the main menu available.
Something similar does already exist. If you have a node name without CamelCase you can set it as a link during writing by putting it inside of 2 squared brackets (e. g. [[Linux]], if a node with this name does exist. There is no option for that, and I do not see, why it should be made as an option.
The problem is only CamelCase, as this works without the 2 brackets and is a little bit uncomfortable to undo.