I will clarify my objections to paywall sites
A) they use publicly and often freely accessible records and trun them into payable documents
B) they claim undue copyright, public records are per definition never copyrighted
C) they unduely collect money without providing the promised service and refuse refunds
Why do i suggest that wikitree removes the HTTP-links from references and that wikitree reduces their "value" to unverifiable indications", because the LINKS are the bread and butter of these paywall sites. the more links you put in your records the more money they earn , on other words the mebership contributions they earn from their paywall is not their main source of income,...
When I state that a "valid reference" is a document I can consult then i mean that i can go to a library/archive and consult the document, if that library/archive is not in my city, i can go to the national library/ national archives, and yes i might have to go there physically.
If want a US book i can consult about every published book in the library of congress. In The UK I can use the national library and the national archives
My opinion is that I don't like paywall operators, cheating leeching companies, that leech money from people who do research, don't provide the services they promise ( no value for money), they don't tell me how they earn their money besides membership contribution, neither what they spend their money on, but clearly they earn a lot more money , they are cheaters that promise fake free weekends but charge you anyway and don't reimburse you, and hide in jurisdictions and legal constructions where they cannot be prosecuted.
IMHO no linking and transscribing ... don't be fooled by fake copyrighting