Selection of generated text (by CSS :before) looks wrong

Binary package hint: firefox-3.5

Please view the attached file and "toy" with selections by mouse. Notice the CSS :before style.

Expected result: consistent behavior of the b's: either always ignore or always select.

Actual result:
1. When I drag the mouse slowly, the b's are not selected.
2. When I drag fast, in some arbitrary lines the b's appear selected.
3. When I select a range by: mouse-click (and release); press shift; press keyboard arrows - the b's are not selected.
4. When I select a range by: mouse-click (and release); press shift; mouse-click somewhere else - the b's in the range appear selected.
5. When a selection is active, removing the focus from the Firefox window makes the b's within the range appear selected.

However, copying and pasting show that *in all the cases* the b's were not selected.

Note: also happens in Firefox 3.6.8

ProblemType: Bug
Architecture: i386
Date: Mon Sep 6 01:43:23 2010
DistroRelease: Ubuntu 9.10
Package: firefox-3.5 3.5.9+nobinonly-0ubuntu0.9.10.1
ProcEnviron:
 LANGUAGE=en_US.UTF-8
 LANG=en_US.UTF-8
 SHELL=/bin/bash
ProcVersionSignature: Ubuntu 2.6.31-22.60-generic
SourcePackage: firefox-3.5
Uname: Linux 2.6.31-22-generic i686