I found this example sentence in Pleco's dictionary entry for 厲害 :
他的聲音真的很厲害。His voice is amazing.
Why isn't 真的 included in the translation to make it "His voice really/truly is amazing"?
More broadly, is it okay to double-up intensifiers (such as 真的 + 很)? If it is allowed, what effect does it have on a sentence's meaning?
E.g. 他的聲音【真的很】厲害 vs. 他的聲音【很】厲害