I actually did that on the first Memorial (1987) after I was df'd (as I have told already, I had partaken as a JW along with a friend of mine the previous year, and we were both df'd for apostasy in the following weeks -- although the Memorial was never mentioned in the process). I went to a nearby KH in Paris, was not recognised at once (I had grown a beard in the meantime :)), and left peacefully when the meeting was over (I suppose some understood who I was but did not step in).
At that point I sincerely didn't mean it as a provocation but as a kind of "testimony" and "souvenir" -- I had joined a church since, but I had not forgotten my previous "spiritual family" in spite of the organisational rejection. Of course I now realise it was completely useless. The next year I didn't bother about the JW memorial anymore...