Public Comment is a vital part of our multistakeholder model. It provides a mechanism for stakeholders to have their opinions and recommendations formally and publicly documented. It is an opportunity for the ICANN community to effect change and improve policies and operations.
.lan, .local, and .internal would all be appropriate options.
The benefit of .internal is that it is much less likely to be already currently deployed across internal network services currently. .local can be seen at the local domain level quite frequently. With that in mind, .lan is much shorter and still well understood by most.
It was mentioned in the proposal that .internal carries the implication that it is never accessible to external processes and could be misunderstood, however due to the relative common knowledge that 192.168.0.1 and 192.168.1.1 are often internal IPs, is less explicit than .internal.
.lan would at least allow for the consideration by those with more technical knowledge that not all .lan applications involve isolation from WAN.