Speaking of Turing complete text editors, here's a Turing Machine implemented in TECO by Marvin Minsky in 1981, that I once ran across in home directory on ITS. (Thanks to Harold Ancell (hga) for saving it and posting it!)

https://news.ycombinator.com/item?id=10161002

    [ I've interpolated the non-printing characters as displayed 
    by (Gnu) EMACS, escape is ^], ^^ is one character, as is \356: ]

    i1Aul qq+^^0:iqm^[29iiq\356y0L1 00L1 11L2 A1L1
    y0L1 0yR2 1AR2 AyR6 yyL3 00L0 1AL3 A1L4 yyL4 0yR5 11L7 A1L4
    yyR5 0yL3 1AR5 A1R5 yyR6 0AL3 1AR6 A1R6 y0R7 0yR6 11R7 A0R2
    ^[j<sR^[;-d-2ciql-^^^[ci"ed^^^[cii^[ciuq'^[>
    j<sL^[;-d-2ciql-^^^[ci"ed^^^[cii-2c^[ciuq'^[>jxblx1lx2lx3lx4lx5lx6lx7hk
    iyyAyyAyy^[32<i0^[>ji110101110000010011011^[ 1uq<htmbqq=>