The main issue seems to be that it is British. There is a strong anti-British sentiment in NL as well since Brexit.
In addition the pro-EU/German press have been telling people for years that the UK will wither outside the EU and even that there would be medicine shortages in the UK. Now immediately after leaving, the UK is drastically ahead in its vaccination programme. Some European politicians reacted to the UK buying up the supplies in advance by spuriously claiming that the vaccine doesn't work. As a consequence there's now quite some shock in German society about this state of affairs.
https://www.telegraph.co.uk/news/2021/01/28/best-advertiseme...
One important thing, though, is that the amount of information in a comment makes a huge difference. Information (that is, new information that people haven't already heard many times) acts as flame retardant. If the GP comment had contained that, I wouldn't have posted a moderation reply.
By contrast, when a comment brings up an inflammatory topic in a one-liner sort of way, it leaves a lot more scope for people to project their own interpretation onto the comment, and what drives such projections are often their own strong feelings about the divisive topic. You can see this in the flamewar direction the thread took here: https://news.ycombinator.com/item?id=26229255.
The main thing to consider in terms of comment quality is the expected value of its future subthread. Having more information in the root comment increases this. Low-information comments about inflammatory topics have low expected value. https://hn.algolia.com/?dateRange=all&page=0&prefix=true&sor...
I don't think that plays much if any role in German public perception. There is no negative association with the British there.
I don't know how well you can actually compare these 2 numbers and if those are even the most important numbers, but that's part of the problem: Most people only look at these numbers and that's why they would prefer the Moderna vaccine.
The problem is that a major newspaper misunderstood the efficacy statistics, and now you've got many, many people who believe AZ has barely an effect.
Obviously this is a hugely popular opinion with the "Querdenker" who are a loose mishmash of covid deniers and "I want my kid to go to school, let those old people die".