I want to echo the subject of this thread. Have just published my first geocache (it's an earthcache, with a good deal of information included), and all I see on the listing is a great, ugly blob of text. I know HTML, and I've tried to directly edit the source (view - source), copy and paste to the source, copy and paste to the displayed text, and GOK what else. Yes, the HTML option box is checked.
Other than directly typing text into the existing text blob, I can make no changes to it. Obviously, just tying in more text just makes the blob bigger.
The FAQ for putting HTML into the write-up merely appears to be a very elementary discussion of some tags -- there doesn't appear to be any discussion of what the mechanism itself is.