I can chime in on this topic. Dr. Andy Cutler would disagree with the ideas that mercury is methylated in the body (naturally or by the yeast) and that yeast holds onto mercury. Everything he mentions online and in Amalgam Illness that applies to me has been spot on, so I'm inclined to accept what he says.
Here are some of the relevant posts through onibasu.com:
The post about mercury not being held by yeast is in the AMC group, dated Aug 19, 2008 19:45:36 (GMT).
The thing I wish Dr. Cutler could have done is warn readers more prominently in AI about the danger of yeast overgrowth. But I cannot complain; he provided background and solutions and I'm happy to finally understand what's been happening to me over the past 18 years. Now if I could just overcome this flare-up...