In the right column of Unanswered | my tags sub-tab I see six tags:
But my list of favorite tags is very different: it has over 50 tags but does not include real-analysis, linear-algebra, analysis, or [believe it or not] homework. Meta.SO post How to remove some of "my tags"?, the answer given there, and the experience of commenters on this post suggest that what I'm seeing is not normal behavior. The "my tags" list should be auto-populated only for users without favorite tags; for others it coincides with the list of favorite tags.
Accordingly, I'm retagging this post as bug.
fourier-analysis
is indeed among my favorite tags. However, so isdifferential-equations
, so this does not explain why FA beat DE. Also, I have over 50 favorited tags, so the software shouldn't feel the need to add its own. $\endgroup$