Specifically, if diary Tom Riddle had succeeded, how would he have strengthened the present day Voldemort?
In If diary Tom Riddle had succeeded, would there have been two Voldemorts?, @Pearsonartphoto gives a quote from J.K. Rowling in his answer regarding what would have happened if Tom Riddle had succeeded in fully manifesting from his diary memory form to a full human form.
Q: In Harry Potter and the Chamber of Secrets, what would have happened if Ginny had died and Tom Riddle had escaped the diary?
J.K. Rowling: I can’t answer that fully until all seven books are finished, but it would have strengthened the present-day Voldemort considerably.
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As well, I've read all seven Harry Potter books many, many times and I haven't been able to ferret out any overt details regarding exactly how the present day Voldemort would've been strengthened by co-existing with diary Tom Riddle.
Specifically, how would the reincarnation of 16-year-old Tom Riddle have strengthened the 67-year-old present-day Voldemort at the time of Chamber of Secrets?
★ I would love an answer from canon, any of J.K. Rowling's interviews, or Pottermore, or an answer constructed within the spirit of canon.