[latexrefman] 1 space between \write and @var{number}

[Karl Berry]

    for the change is that in info format there is a risk of

Not just info format. All formats.

    Indeed we don't want to encourage the user to insert unnecessary
    spaces

It's trying to make the synopses clear. If a reader is likely to be
confused, I think they'd be much more likely to type "\openinnumber",
which is a lot worse than an extra space. The font change would 
be easy to fail to see.

Besides, it's a reference manual. Readers are mostly going to know that
spaces are ignored after control sequences, and if they don't, well, no
harm done.

And finally, sometimes those spaces are aesthetically desirable, in the
eye of the beholder.

    In such a case wouldn't it be more appropriate to insert @IXPS{}

No. --thanks, karl.