Inconsistent size of ASCII graphics as index initials

[Gavin Smith]

Nonalphanumeric ASCII graphic characters, like "@" and "^", can appear
as initials to categorize entries in an index, but I noticed that they
don't seem to have a consistent size. Looking at the "Command and
Variable Index" for the Texinfo index, first I thought that the { and
} were too small, but then I thought that maybe the \ was too big: the
/ is also big. @ is also huge and ^ and ~ are just smudges.

Is this just a consequence of the fonts being used or is something
else going on?

I tried the following test file to see what they looked like in normal text:

\input texinfo
@setfilename

!"#$%&'()*+,-./ :;<=>?  @@ [\]^_` @{|@}~

@bye

and the braces looked comparable in size to the slashes, unlike the
case with the index initials.