I think the point is about ensuring that there isn’t a mismatch between the claims of authority you employ (or, if you have any degree of fame/recognition, the degree to which you temper any public perception of authority you may have) and the actual degree of expertise you have on the topic being discussed.

Here on Reddit, unless you claim expertise you are just another rando commenter, and even if you do claim expertise people are likely to be skeptical due to the anonymous nature of discourse here.

But using your academic credentials or public recognition as an expert to bolster your standing — particularly in non-anonymous settings — despite lacking direct expertise in the topic is another matter altogether.