Jeff King [off-list ref] writes:

I think what happens is that the config editor runs
through the files linearly, munging whatever lines necessary for the
requested operation, and leaving everything else untouched (as it must,
to leave comments and whitespace intact). But it does not keep a
look-behind buffer to realize that a section name is now obsolete (which
we don't know until we get to the next section, or to EOF). In the worst
case, this buffer can grow arbitrarily large, like:

  [foo]
  # the above section is now empty
  # but we have to read through all of
  # these comments to actually
  # realize it
  [bar]

If we treat this case as having a bunch of comments that make the
section non-empty, then we both avoid needing an arbitrarily large
lookbehind and deleting the user's precious comments...

I.e. the rule would be that we only delete the section if there is
nothing but whitespace until the next section header.

-- 
Thomas Rast
trast@{inf,student}.ethz.ch