rocknbil - 5:11 pm on Mar 8, 2012 (gmt 0)
In terms of semantics, I "kind of" agree with them, regardless of the spec. An <li> should be a "list of items" and shouldn't contain paragraph elements, headings, etc. but according to the spec it's perfectly legal. In the same way, a fieldset implies a set of fields by it's very name - even though your usage is perfectly "legal".
That's just opinion though - the bottom line is that if you want to use their service, you need to follow their specifications. You can do a global search and replace to use some other element, can't you?
Another tact would be to just wrap it in an empty form element with empty actions (seems kind of silly but might be a quick fix.)