A good format for a new topic is "dissertation followed by discussion":
start with a brief, factual introduction
then bring on the opinions.
When a discussion dies down and the page becomes static, feel free to refactor mercilessly:
fearlessly edit down to capture the key points
reduce the noise without losing the facts or the flavor
if you merge or delete comments, you can group list "Contributors:" at the end of the page
That's how Wiki content matures and grows in value over time.
For external site links, you can type URLs directly into the text - http://etcete.ra/... - it'll clear to anyone where they're headed on click.
TWiki is international, and an international standard date format like 01 Sep 2001 is preferred. A date like 9/1/01, can mean either January or September, depending on the local conventions of the readers. For months, use the first three letters: Jan, Feb, Mar, Apr,...
Look at the source when you want to find out how something is formatted: click More on the lower toolbar, then checkmark Raw text format and click on [ View revision ]. A bit of HTML experience can't hurt, but you'll soon see with TWiki how far that is from necessary.