> The following occur in _Hart's rules for compositors_ 39th ed. (1983) 142:
> (b) One single-line note on a page should be centred;
> two or more single-line notes on a page should be
> ranged on the left, the whole being centred on the
> longest.
> (c) A short note may be set complete in the break-line
> of another note provided it is set full right, preferably
> with more than three ems between the notes.
> (d) Short notes may be run on in the same line with
> preferably at least 3 ems between them, the line being
> centred. Where there are several short footnotes,
> they should be ranged in columns with a minimum
> of a 3-em space between the longest lines in the columns.
> __________________________________________________________
> How much of this could be automated for LaTeX?

Before looking at this form of the question, first answer the following:

 How much of this could be automated?

ie express it as an algorithm or at least as a set of constraints that
must be satisfied.

My feeling is that this first stage is the tough bit (but
not impossible); without it deciding whether it is reasonable to
implement such a set of rules in TeX is impossible.