You're currently applying a "bugfix" class to the stream-container div under the candidate-discussion-stream div in the Discussion tab for users of non-Chromium browsers (e.g., Firefox). Part of the bugfix class is a CSS rule that nominally flips the entire column [transform: scaleY(-1)], which has the unfortunate side effect of causing the column to scroll backwards (e.g., a mouse scroll upward scrolls down instead).