Bob,
You will not only get your hand slapped - and hard - if you do that, it probably will not even do anything. I don't believe that the font tag is supported at all!
First, the font tag is not even part of HTML any more. It was deprecated in HTML version 4 and I believe is not supported at all in HTML 5. Even if you use it on a web page and declare HTML 4, it is likely to be ignored by newer browsers.
Next, you should be aware that the editing page we use is not an HTML page. The content goes into a database where it is stored as text (the same way we write it). At delivery time, the HTML code to produce a web page is wrapped around the database content by WikiTree's software. That software interprets tags (and other symbols when used in specific ways) and knows what HTML tags to replace them with. The code we enter is not HTML at all, even though many of the tags look a lot like HTML tags. What we use here is called "wiki code", which I think of as a hocus-pocus kludge. This is a fact of life - like it or not, we need to just accept it and move on.
Sorry to be the bearer of such bad tidings.