The markdown syntax states that emails are written with html entities, but in ikiwiki only one part is encoded as it. For reference see http://daringfireball.net/projects/markdown/syntax#misc.
In the HTML page I get this:
while it the href="" attribute should also be encoded.
I don't really see this as a serious issue, because if I were working for a spammer, I would include entity decoding in my web spider that searched for emails. And I could do it easily, as evidenced by the code in the htmlscrubber that doe it. So I assume this technique is not very effective at blocking spam. --Joey