What does rebel infighting mean for Syria conflict?

BBC News - What does rebel infighting mean for Syria conflict?: 

"There is already one other war-within-a-war going on in Syria, as the Kurds in the north-east assert their control over areas where they predominate, clashing daily with Islamist and other rebel groups.
Will the vicious fighting with ISIS become entrenched as a third ongoing conflict, draining the rebel movement and distracting it from its primary mission of confronting the regime?
What [ISIS] has been doing... is exactly what the regime was doing -detaining and killing activists, torturing people, and crushing freedom in general”
The clashes, raging over a wide swathe of territory in at least four provinces - Hama, Idlib, Aleppo and Raqqa - raise many other questions too."