People claim that you should not assign VLANs to SID0. However I have not found any examples of what can go wrong in the worst case.
It is clear that having a VLAN assigned to SID0 = CIST will make link changes concerning that VLAN have the entire spanning tree (all regions) recomputed. Having properly assigned the VLAN to an MSTI other than 0 would have limited the recomputation to the concerned region only.
What else can go wrong?