User blog comment:DrCeasium/Hyperfactorial array notation: Analysis part 2/@comment-5529393-20130527105642/@comment-7484840-20130530144401

The rule does terminate, because [@m...m@]w/q = [@m,m,m,...,m,m@] with q m's (notice lack of w/), and the righter arrays in the chain will (very slowly) decrease. As for what happens with the ...'s, when w/[q@] is used to expand m...m to a string of m,'s, the w/[1@] will remain there, and when the m,m,m...,m from the w/[q@] to w/[1@] change has been removed by evaluating the array, work on the [1@] until it is in the form [p@], and then put another string of m's, this time of length p, where the m...m was at the start.

Put another way, the w/[@] will not just produce one string of m,m,m,m,...; it will produce one, then when this is gone, it will produce another (of much longer length due to the effect of the last lot of m's having been used), and then when this is used, another, and another, until the array to the right of the w/ is used up completely, and the w/ removed.