Creole covers markup for some CommonTextElements. The markup should be EasyToLearn and EasyToTeach, as well as FastToType and should use ReadableMarkup which is NonDestructive. It should cover the CommonThingsPeopleNeed.
Because we want Creole to be widely adopted, we need to make it easy to parse using CommonWikiParsingTechniques, and also easy to explain, preferably using a prepared simple CheatSheet. The both goals easy to explain and easy to parse sometimes contradict each other. It is generally good practice for developers to listen to their users and MakeTheMachineWorkHarder in that case. On the Ambiguities page we collect possible markup colissions and strategies to handle them.
There are HintsOnExtending that are supposed to help adding non-standard features to Creole when needed.