All HTML tags are supported, but use the CSS (wp-layout.css).
Which blog address are you using ? I just checked Binary Bonsai and it looks great.
index.php looks for wp-layout.csss in the same directory as itself, so if you have moved the CSS, then alter the address in the main index.php template.
For comments the allowed tags come from kses.php, which with 1.1 you can overwrite in your my-hacks.php file.
Where in kses are the tags? How do I figure out why it isn’t working?
Which version of WP are you using? There were some bugs in 1.0 with the allowed comment tags, which were fixed in 1.0.1. 1.1-beta has some additions as allusion said for overwriting what is allowed.
