I'm not seeing any explanation behind any of your attestations. Are they assumptions?

Saying conflicts are inevitable/unavoidable between name systems seems simplistic: it's a problem to solve. Not necessarily easy, but I know of no hard law making it implicitly insurmountable.

Why does changing name system destroy all value? Sure, changing any system is disruptive and can be relatively destructive; such changes must be weighed against benefits of change, but I see no reason choosing generally better alternatives must destroy all value.

The conflict is intuitively obvious. A name system maps names _to_ something. If system A and system B have the same mapping, that's just the same system under a different name. If they have different mappings they conflict because the mapping will give me different results from system A versus system B. It's that fundamental.

The address bar in Chrome shows both the string as a potential search, and URLs in recent history/tabs with that string. Why wouldn't a Handshake-supporting browser do something similar?

Most alternative domain name systems nest everything under a single TLD – .eth, .onion, etc. In theory, either the standard DNS or a different alternative name system could cause a conflict by using the same TLD themselves. But unsurprisingly, ICANN/IETF are a lot more receptive to "please avoid using this one semi-branded TLD" than "please hand over the entire namespace to us". .onion is already formally reserved by IETF RFC as a "special-use domain name", and hopefully .eth will join it in the future. As for a different alternative name system, conflict over .eth could theoretically happen if Ethereum forks again or if ENS itself is somehow forked, but an independent effort would presumably pick a different name.