This rewrite would push a UnaryOp[not] through an EvalFilter under certain conditions. For example UnaryOp[not] EvalFilter PathCompare[eq] Constant[2] --> EvalFilter PathCompare[neq] Constant[2]

This is not always correct when the path below the EvalFilter contains a Traverse. For example, the following rewrite is not correct: 
UnaryOp[not] EvalFilter PathGet["a] PathTraverse[1] PathCompare[eq] Constant[2] --> EvalFilter PathGet["a] PathTraverse[1] PathCompare[neq] Constant[2]

This would have incorrect behavior for arrays at path "a".