The concept of Vaccine-induced enhancement is pretty frightening as well, See links below:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7131326/
https://www.pnas.org/content/117/15/8218
The first article is from 2009, and describes the general concept of antibody-induced enhancement. Antibodies are produced against the virus in a first infection (or vaccination), but when a second infection occurs, the antibodies attach to the virus and actually make it easier for the virus to cause disease.
This doesn't happen often, but it's known to occur to those who get dengue. Dr. Griffin mentioned this in July.
TWiV (This Week in Virology) #635, recorded July 5
These are my notes of Dr. Griffin's talk, so I can't guarantee they're accurate. If you have questions, go listen to the podcast.
Possible reinfection. With some other viruses, a second bout is worse than the first. Earlier in the epidemic, cases that were initially thought to be reinfections were probably just two phases of a single infection. But we’re still not sure if it was reinfection, or how quickly reinfection would occur.
With some other viruses, a second reinfection is often more severe. Dr. Griffin himself caught dengue in China in the 1980s, easily recovered, then got it again in Zimbabwe. He was so sick the second time that his parents were told “We’ll let you know if he’s still here in the morning.” Well, obviously he recovered, but we don’t know what will happen with covid, so it’s foolhardy to assume that reinfection would be mild when it could potentially lead to tragic consequences.
The second article you link is from April of last year, when scientists were just starting to work on a vaccine, and the possibility of virus- or antibody-induced enhancement was on their minds.
But in the time since then, there hasn't been any evidence of this sort of enhancement in those who've gotten reinfected, so it seems extremely unlikely to be relevant to Covid.
https://www.chop.edu/centers-programs/vaccine-education-center/vaccine-safety/antibody-dependent-enhancement-and-vaccines