Fragment identifiers in data URIs

Hello,

I tried to find documentation about fragment identifiers
for data URIs, but haven't discovered any so far. RFC 2397 seems to be
quiet about the very possibility to have such identifiers. It's only
noting, that "data" is specified as "uric" from 2396
(which happens to exclude "#"). Therefore it seems, the behavior
of this is undefined:
   
data:<h1>%20id=%22FOO%22>ABC</h1>#FOO
I tested Firefox and Chrome, and both react differently, Firefox cutting
off the data: URI at the hash, Chrome just outputting it and the the
rest.

A normative rule would be great. One use case: SVG
filters embedded in CSS stylesheets. CSS filters can be used like this:
    filter: url(svg-url#element-id);
But we cannot address them, when the SVG is embedded as data URI:
    filter:
url(data:image/svg+xml,.....id="FOO".....#FOO);
Cheers,
 Manuel