I have never been reviewed for any HTML game, but this is something that does happen with Kiss the Mortog and I believe it can happen with Double or Nothing as well. Much like flash games, they check the time it took you to obtain such a score. This is why greasemonkey scripts have the random delays into the script. Personally, when I use dice-a-roo and sahkmet solitaire autoplayers, I lower the delay significantly because I've never ran into any issues with those games.
Unfortunately, I can't give you any solid advice on this from experience. I would assume that the Greasemonkey script should use a delay between 1200-1500ms which is about 1.2 - 1.5 seconds inbetween clicks. Depending on the amount of plays and what data TNT uses to catch us on HTML games, I'd say it could go either way. When I play Double or Nothing legitly, I just click randomly and I'm sure I click much faster than that. However, I don't play for a half hour at a time either.