also i'm wrong; it doesn't have an option to compile with readline, just libedit (which indeed is not included in the debian package configuration). the incantation was as follows:

    : Downloads; apt-get source dash
    : Downloads; cd dash-0.5.12/
    : dash-0.5.12; sudo apt install libedit-dev
    : dash-0.5.12; ./configure --with-libedit
    : dash-0.5.12; make
    : dash-0.5.12; src/dash -E

libedit supports ^r but not ^o

on the other hand my dash process with libedit is 1.3 megs rss while my bash process is 7 megs rss. and the dash executable is only 130k. still, bash is only about 20% slower to start up