Commas are very often a judgment call. I'd say that the comma enhances the first sentence but serves no real purpose in the second, other than to distract. The reader will unconsciously pause at the comma, and the pause in the first sentence emphasizes the "tallness" of the building (which is helpful to the overall description). The comma in the second simply interrupts the flow of a familiar description.
– Hot LicksMar 08 '15 at 13:29
You wouldn't say "the brown big bear" or "the gray tall building", so the adjectives are *not* coordinate, and you don't need a comma. See the answer in my previous link.
– Peter Shor Mar 08 '15 at 13:31
That's where the confusion lies. We wouldn't say 'The tall AND gray building is my company"; nor would we say 'The big AND brown bear scared the children.' To me, then (I think), the comma should be omitted in both because it doesn't pass the test for differentiating between coordinate and cumulative adjectives.
– whippoorwillMar 08 '15 at 13:34