email spam filtering does not "see" email addresses when they are NOT preceded by a word

By accident I found out that (some) of the emailadresses in (at least) pages in one of my drupal sites weren't filtered/hex'ed up with the javascript option.

The problem seems to be related to recognizing the start of an emailaddress. Since I couldn't make sense from the reg-exps in the filter.inc, I can't really say if this can be fixed or not. I do think, however, that this should not be behavior by design, because it will have people assume incorrect things.

Steps to reproduce
1) Stock Drupal 4.5.1 with BBcode 4.5.0; filtered HTML input format with BBcode + other default filters (html, legacy, line break) enabled.
2) Create new page, with a random title and as body (remove quotes) "X info@drupal.org".
3) Preview.
4) View source of page and see that the address is hex'ed up.
5) Remove the X (leave " info@drupal.org", note the space after the initial quote).
6) Preview.
7) View source and and experience that the address is NOT hex'ed up anymore.

Optional:
8) Remove space, leaving "info@drupal.org".
9) Preview and view source, again no hex'ing up of the email address.

Ad. 1. Other filters, like urlfilter, quote or smiley filter, can remain enabled. They do not influence the bug.

The preceding word requirement doesn't seem necessary to me because I discovered the bug in a sentence like "To find out more about drupal mail those people (info@drupal.org)" in which the address is not hex'ed up.

Note, I flagged this as critical because it can cause people to falsely think that the emailaddresses they publish are harvester-bot protected.