Here is an example:

[provisioning@MikroTik] > /interface wireless print terse
0 name=wlan1 mtu=1500 l2mtu=1600 mac-address=xx:xx:xx:xx:xx:xx arp=enabled disable-running-check=no interface-type=Atheros AR9300 ...

I think interface-type=Atheros AR9300 should be interface-type="Atheros AR9300"

Found more examples of unquoted output with spaces:

ssid=cats and boots area=""
wpa-pre-shared-key=cats and boots wpa2-pre-shared-key=cars and clowns

How can we reasonably parse these?

Ok, this does not address the interface-type bug, but the workaround for SSID and pre-shared-key is to not use "terse" mode. The values are quoted in the normal output.