Your links kept me reading and reading.
I also did a search on Thimerosal. Yes, it's in there as a "preservative", neccessary becuase the nature of vaccines themselves are bits of dead "proteinaceous" life forms, and , as such, are prone to rapid decomposition (bacterial, fungal) if not "stabilized".
The "active ingredient" definitely is ethyl mercury. Mercury salts and other preparations are as a rule less toxic than the organo-Mercuric compounds, but that is a misleading statement. Take for example, Mercurous chloride (Hg2Cl2,calomel in Calamine lotion, relatively low toxicity) compared to Mercuric Chloride (HgCl2, a violent poison).
Well it's not my point to try to explain the chemistry of mercury here, just that in some preparations it seems to be the best preservative known. However, alternatives are being used due to the controversy over the use of ANY mercury compounds in humans.