Appearance items below get expanded / unfurled when anything changes in the panel
Assign many fills to a path using Appearance.
Do anything with anything in the panel: change a color, assign an effect, add another fill.
Fills below the current one get unfurled.
These could be fills just below the current view of the panel, 'below the fold', as one of the attached GIFs show, or all the fills below the last unique one, as in the second GIF.
I’d test more, but the fact we can’t collapse all the items in the Appearance panel (which is possible with Opt/Alt in Layers!) makes me extremely irritated — so I made a request to allow this as well: http://illustrator.uservoice.com/forums/333657/suggestions/49257572
UserVoice has many more reports and requests about Appearance being underdeveloped. I do my best to crosslink these, but don’t hesitate to just look for these here: https://illustrator.uservoice.com/forums/601447-illustrator-desktop-bugs?category_id=209074 and here: https://illustrator.uservoice.com/forums/333657-illustrator-desktop-feature-requests?category_id=209482
So sad Teri Pettit no longer works at Adobe :(
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Ton commented
I remember complaining about it in 2011 at the prerelease site (can't find it anymore). But there are many fills with an offset path effect that expand in the Appearance panel after saving this file.