I recently heard of [name_f]Marcella[/name_f] pronounced [name_f]Mar[/name_f]-chell-a for the first time, and though I prefer [name_f]Mar[/name_f]-chell-a, I was wondering if anybody pronounced [name_m]Marcellus[/name_m] [name_f]Mar[/name_f]-chell-us? And what do you think of the nickname [name_u]March[/name_u]?
I’ve never heard either name pronounced that way. I’ve always heard it at mar-SELL-us, and tbh I only think of “chicken marsala” when I hear these names. [name_m]Marcellus[/name_m] is NMS and I think most people will pronounce it differently than you’d like.
I would say [name_f]Mar[/name_f]-SELL-us in English speaking countries, [name_f]Mar[/name_f]-CHELL-us in [name_f]Italy[/name_f] 
Although nn [name_u]March[/name_u] I think is appropriate for either.
I would say mar-SELL-iss. I think [name_u]March[/name_u] would work well for either, though a bit better for mar-CHELL-us.
I pronounce mar-sell-us. I live in the US.
I was surprised when the Netflix show pronounced [name_f]Marcella[/name_f] (mar-chell-a).
I initially read it as [name_f]Mar[/name_f]-sell-us, but when it comes to saying it out loud I think I would say [name_f]Mar[/name_f]-chell-us, as it is an Italian name
I agree 
I say mar-SELL-us, as I say [name_f]Marcella[/name_f] mar-SELL-ah.