How to properly typeset footnotes/superscripts after punctuation marks?

Question

I find the spacing of footnote marks after punctuation marks quite unsatisfactory, especially with sans serif fonts and compared to the spacing after letters. Example follows:

I came up with a little macro myself that tries to amend this manually.

\documentclass{article}
% URW Classico is a font that makes the issue apparent
\renewcommand{\sfdefault}{uop}
\renewcommand{\familydefault}{\sfdefault}
% define punctuation-aware footnote macro
\newlength{\punctuationfootlength}
\newcommand{\punctuationfootnote}[2]{#2\settowidth{\punctuationfootlength}%
{#2}\hspace{-\punctuationfootlength}\footnote{#1}}
% define a very small type area and don't care about margins
\setlength{\textwidth}{150pt}
\setlength{\textheight}{5\baselineskip}
\begin{document}
\noindent The three little pigs built their houses
out of straw\punctuationfootnote{not to be confused with hay},
sticks\footnote{or lumber according to some sources} and
bricks\punctuationfootnote{probably fired clay bricks}.
\end{document}

This will look like this:

I have to say, I didn't like this either. So I fiddled around a bit and set back the footnote marks by a half

and a third of the width of the punctuation mark.

Personally, I like the look of the last (-.3\punctuationfootlength) the best. But I'm a bit concerned that nobody ever seemed to have shared my opinion on this and if anything put a hair space between a letter and a footnote mark but never decreased the kerning. So if any typography guru here could put me straight on this matter that would be great. I'm also happy about anyone's second or third opinion on this.

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Edit: Originally I also asked for a better way to TeX this here. As this is a separate question however, I moved it here.

Edit 3: That question led to a new package, fnpct, which should be used to automatically adapt footnote kerning in your LaTeX document.

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Edit 2: Jon's comment caused me to succumb to the temptation I had all along of trying an additional intermediate between solutions 2 and 3. It seems like a ridiculously small change but here is -.4\punctuationfootlength:

Can't decide though. After a bit of pondering, I think I like the 3 a bit closer than the 1 which doesn't make things easier I guess.

Answer 1

(Obligatory Bringhurst reference warning)

Bringhurst has a few challenging comments about footnotes, including a mild "don't do that", but the relevant one for this question is (The Elements of Typographic Style, v3.2, pp68-69):

4.3.2 Check the weight and spacing of superscripts. ... "Superscripts frequently come at the ends of phrases or sentences. If they are high above the line, they can be kerned over a comma or [full stop], but this may endanger readability, especially if the text is set in a modest size."

Answer 2

I guess I'll use a .06em hair space before all regular footnotes as suggested by http://www.read.seas.harvard.edu/~kohler/latex.html (referring to Jan Tschichold) and a negative hair space for punctuation footnotes (actually the link suggests a .08em hair space and .3\punctuationfootlength miraculously turned out to be .0828em but still …). This comes close to the manual kerning I felt best about

The three little pigs built their houses out of 
straw,\hspace{-.06em}\footnote{not to be confused with hay} 
sticks\hspace{.07em}\footnote{or lumber according to some sources} and 
bricks.\hspace{-.08em}\footnote{probably fired clay bricks}

Talk about putting paper between cast metal sorts …

All together this yields

\documentclass{article}
% URW Classico is a font that makes the issue apparent
\renewcommand{\sfdefault}{uop}
\renewcommand{\familydefault}{\sfdefault}
% define punctuation-aware footnote macro
\let\origfootnote\footnote
\renewcommand{\footnote}[1]{\kern.06em\origfootnote{#1}}
\newcommand{\punctfootnote}[1]{\kern-.06em\origfootnote{#1}}
% define a very small 
\setlength{\textwidth}{150pt}
\setlength{\textheight}{5\baselineskip}
\begin{document}
\noindent The three little pigs built their houses out of
straw,\punctfootnote{not to be confused with hay}
sticks\footnote{or lumber according to some sources} and
bricks.\punctfootnote{probably fired clay bricks}
\end{document}

which looks like this:

This should also resolve the debate about the order and number of arguments since \punctfootnote became a drop-in replacement for \footnote.

Thanks a lot for your input! Of course further comments are still very welcome.