This is as much as I can determine. Based on Confederate service files at the National Archives, records of Co D, Gray's 28th Louisiana Regt, do include a sergeant named Tippett on roll. However, his name is Andrew J Tippett, not John L Tippett. Company records also include Lieutenant Simons as mentioned earlier. Service files do report of what became of either Lt Simons or Sgt Tippett during the war.

Checking Ancestry family trees for John Tippett using Texas as a place of residence, nine family trees give John L Tippettt's dates as 1846 - 1897, usually with specific date of birth and death. None have post-war sources. However, I didn't see a source cited for the reference you have that John Lee Tippett died during the war, either.

Due to lack of confirmed sources for this young man, we don't know much about him after the 1860. I can't match him to a Confederate service file or a census record after the war. On occasion, we do find Confederate enlistments at fifteen and sometimes even fourteen. However, except for late war Confederate Junior Reserve units composed entirely of young men under 18, I don't recall seeing a non-commissioned officer on record as young as fifteen.

20-25 years ago, I reviewed 15,000 service files and matched 3,000 to census records for a M A thesis on Confederate recruiting in a specific county. When mentioning my experience, it's based on tens of thousands of service file reviews over the last three decades. Based on the little evidence at hand, I'd guess that a family researcher confused Sergt Andrew Jackson Tippett with John Lee Tippett. And unless something definite about him can be located, we're all just guessing.

I'll be interested to know what you can locate to firm up John Lee Tippett's story.