I got a reviewer's comment on my manuscript that suggests that the most common convention is that tables and figures are not referenced from the Discussion section of a paper. This is something that sounds new to me and I wonder if it's true in some fields (such as biology)?
Every field has a large number of different types of publishing venues with different requirements and expectations for the structure of manuscripts. If the reviewer is making a legitimate complaint, it is likely to have to do with the particular journal that you are submitting to. Some do have very particular requirements about structure and what exactly goes where, so perhaps that is what the comment is about.
Absent particular structural constraints, however, I think that it's fine to reference figures or tables from a discussion section, as one is discussing them (in fact, it would be strange not to do so).