I noticed some unexpected behavior while putting together a minimal working example for a different issue. In a multi-column layout with column balancing turned on, if the first column contains a single line and that line contains a footnote, then the footnote will not be typeset. A minimal example demonstrating this follows:

\starttext
\startcolumns[n=2]
A single line of text with balancing.\footnote{Footnote dropped in column balancing.}
\stopcolumns

\stoptext

I typeset this using ConTeXt version 2020.03.10 (from the TeXLive 2020 distribution).

Clearly, the situation I described is an exceptional one, but it could happen in some real cases (e.g., if the last page of a two-column text consists of a widowed line with a footnote), and in any event, this seems like unintended behavior, so I thought I should bring it to the mailing list's attention.