Yes, this is a special footnote, as it contains an anchored from "at insertion point" which exends beyond the top of the line:
To the left you see the English document, to the right a German one. I have checked for 'same setting' for ¶ format, flow format, etc. Only the language setting is different. I do not see what can cause this overflow indication. BTW it does not disappear with MIF washing.
It also does not depend on what follows nex in the flow (heading, body etc.).
I can live with this, as in pdf it does not appear - and nothing actually is missing on the page. I'm just curious what is going on here.