Did you read till the end? Look at the last section titled "What can you do"; I reproduce the list here.

- Announce the dates of the conference as early as possible (allows participants to book travel, visa appointments, maybe club multiple conferences)

- Provide invitation letters in a timely manner

- Call for participation as early as possible

- Notify speakers as soon as you can

This is a very reasonable ask. Each line is a request asking the conference organiser to do it as "soon as you can", or "timely manner" etc. He is merely asking conf organisers to be cognisant of foreign attendees time constraints.

The text preceding that list is “if … you want a diverse audience”, which suggests they’re asking conference organisers to send personalised invitation letters to every foreigner who wants to attend, not just speakers. That could mean thousands of letters.

Almost certainly not thousands given that most large tech conference attendees are North American and European. But it's totally routine for large conference organizers to provide visa letters for attendees upon request. e.g. https://events.linuxfoundation.org/open-source-summit-europe...

If a person has registered for a conference (which I imagine involves paying money), it’s the responsibility of the conference organizer to provide a visa invitation letter (which can just be derived from a template; doesn’t have to be specialized), as many visa applications require such a letter. Otherwise they should refund the money and not accept applications from foreign participants at all.

Why organize the conference in a country like this in the first place? It's just better all round if organizers choose countries with better (easier) Visa systems than US/EU/UK/...

I know at least one that moved out the US for this reason.