"as befits" or "as befit"

Consider these sentences, please:

1. He writes beautifully, as befits a poet.

2. She was buried in the cathedral, as befits someone of her position.

3. As befits a Quaker, he was a humane man.

These are sentences taken from different dictionaries. As we can see, all of them use the phrase "as befits."

Q: As it is clear from the above examples that the verb "befit" in the phrase "as befit(s)" does not have a visible semantic subject. So, Is it always "as befits", using the singular form of the verb, or do we use "as befit", using the plural form, in some contexts?

Befit means be appropriate for. There is an unspoken subject, it, which is always singular.

It befits a poet to write beautifully.

A little reconstruction may reveal what is going on:

Beautiful writing befits a poet

Cathedral burial befits her

Humaneness befits a Quaker

Hence we may use the plural form to write:

Nobility and courage befit admiration as a hero.

When turned round to mimic the structure of your examples:

As befit nobility and courage, they are admired as heroic qualities.