stutter
ARES System Manual: filter Text Filter Utilities

filter stutter <flags>: Randomly reduplicates consonants and syllables.

Flags format: Specify the severity as 0 (no stutter) to 100 (extreme st-stutter).

stutter is a layer 2 (apraxic) filter. It will be applied to the text after layer 0 and layer 1 filters but before any filters of a higher layer.