I think that theoretically if the planner sees a condition like a.column1 > constant_value, and it also has a condition like a.column1 = b.column2 then it could autogenerate the b.column2 > constant_value condition. And of course > could be <, <=, >= and <>
But I could be wrong, particularly with respect to nulls and how = is mostly the same as 'is not distinct from' except for 'select null = null' being null and 'select null is not distinct from null' being true. Perhaps if either/both columns have a not null constraint, then this could still be done. Whether or not it should be a separate question.
