J is not a weird letter, but English is a weird language. Originally it is the consonantic i, and in many languages it's still used that way. Only because of English and French, J is associated with [d͡ʒ]/[ʒ] (the English J-sound).
In German 'yes' is 'ja'.
Does anyone else love how 'Jes' is also Youth Esperanto Week? I typed that in and it counted me wrong lol. Never use the second definition that it gives you....
I see no reason for it to be in the dictionary (most 2-3 letter words are acronyms).