Wikimedia Bugzilla is closed!

When using wiki-table syntax, under certain conditions the parser introduces extra <p>…
</p> tags into the text in a table cell which negates any attempt to control the 
padding/margin settings and adds extraneous white-space to the cell.

{| class="wikitable"
|| This is OK.
|}

{| class="wikitable"
||
This is not.
|}

{| class="wikitable"
|| This is
just
plain
awful.
|}