How does 再……不过 work?

Question

I'm reading an article about Chinese privacy concerns should TikTok data be handed over to US companies, wherein we have:

事关国家安全，面对任何可能的威胁都必须零容忍。中国人民关心中国的国家安全利益，关注中国企业正当的海外利益能否得到有效保障，这都是再正常不过的事情，也有足够的理由质问美方的动机。
_{人民网三评“TikTok交易”之二：浑水摸鱼，想都别想！，人民网，2020年09月24日}

I'm struggling to understand the grammar logic in the part highlighted in bold. Google Translate translates this to:

这都是再正常不过的事情
These are all normal things

However, 这都是正常的事情 also has this meaning. So it looks like 再……不过 is some kind of grammar structure used to change the tone here, although I didn't find it at the Chinese Grammar Wiki. It seems related to 再好不过 = "couldn't be better / ideal / wonderful".

Question: How does 再……不过 work?

(I believe I found the answer searching the web, so I thought I'd self-answer. I welcome further answers.)

Answer 1

Judging from searching the web, it looks like we're using the grammar structure:

再 + [adjective] + 不过
couldn't be more [adjective]

It adds emphasis to the adjective (turning it into a longer adjective), such as in the given example:

[without the 再……不过]: 这都是正常的事情
these are all ordinary matters

[with the 再……不过]: 这都是再正常不过的事情
these are all couldn't-be-more-ordinary matters

It can be used with a range of adjectives; some examples in the wild are:

再红红不过黎明，再美美不过李嘉欣！^[src]
Couldn't-be-redder dawn, couldn't-be-more-beautiful Li Jiaxin

我其实和你一样,是个再自私不过的人了^[src]
I, in fact, like you, am a couldn't-be-more-selfish person

It is often used in conjunction with a 了, such as in:

我们对结果再高兴不过了^[src]
We, regarding the outcome, couldn't be happier.

鸡腿面包，再好吃不过了！^[src]
Chicken leg bread: couldn't be tastier!

穿阔腿裤不要穿这3种鞋子，再丑不过了！^[src]
[When] wearing wide-leg pants, don't wear these three kinds of shoes: [it] couldn't be uglier.

This function is similar to 太……了 and 及了.

Answer 2

事关国家安全，
Concerning national security,
面对任何可能的威胁都必须零容忍。
any possible threat must be confronted with zero tolerance.
中国人民关心中国的国家安全利益，
Chinese people care about China's national security interests,
关注中国企业正当的海外利益能否得到有效保障，
and whether or not Chinese companies overseas have effective safeguards,
这都是再正常不过的事情，
this is completely normal,
也有足够的理由质问美方的动机。
and also sufficient grounds for questioning American motives.

这都是再正常不过的事情，literally: this all is furthermore (a) normal-not-go-beyond thing