I do think that you have a point there. However it's complicated.

Money quote from your cited paper: "Our data show that anti-disease vaccines that do not prevent transmission can create conditions that promote the emergence of pathogen strains that cause more severe disease in unvaccinated hosts."

However, despite the small odds of a population bottleneck, mutations naturally happen and with "[...] more than a million new infections occurring every day and billions of people still unvaccinated, susceptible hosts are rarely in short supply. So, natural selection will favor mutations that can exploit all these unvaccinated people and make the coronavirus more transmissible." [0].

This [1] nature article from 2020 has a different view on the relation of leaky vaccines, spread control and disease severity; money quote: "Bailey et al. performed transmission experiments using Marek disease virus in chickens and found that the herpesvirus of turkeys vaccine significantly reduced feather viral load in both vaccinated birds and unvaccinated contact individuals. The authors found that contact birds were less likely to develop disease and die, and that they displayed milder symptoms and shed less virus, when infected by vaccinated birds, potentially because of a lower infectious dose"

The article based on current research [2] _also_ examining Marek disease.

So there you are: one probem, multiple views by experts and a bunch of hackernews readers, unable to evaluate the papers.

[0] https://scitechdaily.com/what-is-causing-all-these-new-coron...

[1] https://www.nature.com/articles/s41579-020-0358-3

[2] https://journals.plos.org/plosbiology/article?id=10.1371/jou...