>>>>> On Sun, 30 Jan 2011, Eli Zaretskii wrote:

[Hey, I think this beats the record for the fastest reply I ever got
for a bug report. :-) ]

> I think the reason is that the section names used by the distributed
> info/dir file are different from the section names stated by the
> individual Info files.  Could you perhaps verify that?

Right. If I modify the original info/dir file, such that "Info" is in
section "Texinfo documentation system", "tramp" is in "GNU Emacs", and
all the rest in "Emacs", then I get practically no duplicates.

(The one exception is "URL" which ends up in the strangely named
section "World Wide WebINFO-DIR-SECTION Emacs". Looks like the
duplicate @dircategory entries in doc/misc/url.texi are not allowed.
Trivial patch is attached.)

>> Attached patch fixes the problem for me. I suggest that this should be
>> applied to the emacs-23 branch.

> Thanks.

> However, isn't it better to invoke install-info with the --keep-old
> option?  Does that solve the problem?

That doesn't help, unfortunately.