Why is the calomel electrode widely preferred despite its toxicity?
[&hellip;] Why and how chemist are still able to perform experiments using Calomel electrodes despite its toxicity? [&hellip;]


I mostly used non-aqueous silver electrodes as a reference for my measurements in acetonitrile.

But I wouldn't be afraid to use a saturated calomel electrode (SCE) when necessary. We have recently discussed the toxicity of mercury metal and I think it is largely overrated.

As far as $\ce{Hg2Cl2}$ (calomel), the other mercury component in the SCE is concerned, have a look as the wikipedia article that you have cited yourself. The solubility is extremely low ($\mathrm{2.3\ mg\cdot l^{-1}}$) and the ${\mathrm{LD_{50}}}$ is $\mathrm{210\ mg\cdot kg^{-1}}$ (rat, oral uptake). This isn't overly dramatic either, when compared to the infamous potassium cyanide (${\mathrm{LD_{50}}}$ $\mathrm{5\ mg\cdot kg^{-1}}$, rat, oral uptake). 

Actually, calomel had medical uses :) 

In an article on Venereal disease prevention, the author writes:


  [&hellip;] the absence of therapeutic modalities spurred the United States Armed Services to utilize Credé's solution for urethral irrigation and locally applied calomel ointment for prophylactic purposes in World War I [&hellip;]


As far as the toxicity is concerned, both mercury metal and mercury(I)chloride are by no means comparable with dimethylmercury.