You mean change the hardcoded font name in /sys/src/cmd/acme/acme.c?
No, add something like: font = /lib/font/bit/fixed/unicode.7x13.font fn acme {builtin acme -f $font $*}to your lib/profile. This will set your acme and rio fonts to unicode.7x13.font. Substitute the pathname to your preferred font file, then reboot your terminal.
--lyndon