Isoptope effect on electrophilic aromatic substitution

My book reads 



> 
> Sulphonation will be the most effected electrophilic aromatic substitution reaction when benzene is replaced by hexadeutrobenzene.
> 
> 
> 


I am not able to figure out how. All EAS reactions proceed by formation of an arenium ion and then the loss of an $H^+$ ion to regain aromaticity so all of them should be equally effected ( textbook does not mention how they are effected). I feel the only effect should be due to difference in bond enthalpies of $C-D$ bond and $ C-H$ bond.


I came across this reaction mechanism from [chemlibretexts:](https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Supplemental_Modules_(Organic_Chemistry)/Arenes/Reactivity_of_Arenes/Nitration_and_Sulfonation_of_Benzene)
[![enter image description here](https://i.stack.imgur.com/cHDic.png)](https://i.stack.imgur.com/cHDic.png)
The hydrogen released is taken up by the $-SO\_3H^-$


Can someone explain how and in what ways the replacement of hydrogen by deuterium effects the reaction ?


