Bugzilla comments are plain text - so typing <U> will produce less-than, U, greater-than rather than underlined text. However, Bugzilla will automatically make hyperlinks out of certain sorts of text in comments. For example, the text "http://www.bugzilla.org" will be turned into a link: http://www.bugzilla.org. Other strings which get linkified in the obvious manner are:

A corollary here is that if you type a bug number in a comment, you should put the word "bug" before it, so it gets autolinkified for the convenience of others.

If you are changing the fields on a bug, only comment if either you have something pertinent to say, or Bugzilla requires it. Otherwise, you may spam people unnecessarily with bug mail. To take an example: a user can set up their account to filter out messages where someone just adds themselves to the CC field of a bug (which happens a lot.) If you come along, add yourself to the CC field, and add a comment saying "Adding self to CC", then that person gets a pointless piece of mail they would otherwise have avoided.

Don't use sigs in comments. Signing your name ("Bill") is acceptable, if you do it out of habit, but full mail/news-style four line ASCII art creations are not.

Bugzilla stores comments unwrapped and wraps them at display time. This ensures proper wrapping in all browsers. Lines beginning with the ">" character are assumed to be quotes, and are not wrapped.

On the “Dependency tree” page linked from each bug page, you can see the dependency relationship from the bug as a tree structure.

You can change how much depth to show, and you can hide resolved bugs from this page. You can also collaps/expand dependencies for each bug on the tree view, using the [-]/[+] buttons that appear before its summary. This option is not available for terminal bugs in the tree (that don't have further dependencies).