HI Eric,
The EPM-AddIn documentation does not state any specifics when using the "inputable Member" formatting.
It is used normally when you want specific formatting for your base level member. In BPC you can input date (Save) data only on the base level member not on parent level members data get aggregates on the parent level member. So "inputable Member" formatting will apply only on the base level members.
The formatting for Local Members, Blank Members, Hierarchies etc. is recognized however.
If you are using hierarchies level formatting and inputable Member there are might chances of conflicting formatting,
Better to use either of them and also check check which formatting you are using Row or Column.