Thread: The structure "for + pro(noun) + infinitive" as the subject, is it possible?

The subject of a sentence can never be within a prepositional phrase (in a 'for' clause).

Your tenses also don't sound natural. To invite someone to something and to prompt something are straightforward tasks and I would say they demand the perfect past tense in this context, not the present perfect progressive. Thus,
For us to have been invited to the party prompted in us an inordinate pride.
To have been invited to the party prompted in us an inordinate pride.

The meaning is the same, but 'for us' is not part of the subject. I'll also comment that neither phrase sounds very natural/native. Infinitives are most often used as subjects in habitual/general circumstances (e.g. To study Russian is very difficult). So you could naturally say something like 'To be invited prompts an inordinate pride', but it doesn't sound quite right when you personalize it in the past. If you wanted to use a similar structure that sounds more natural, I would use a gerund (verbal noun), e.g.
Being invited to the party prompted in us an inordinate pride.

I agree 100% with zxc. Although perfectly acceptable from a grammatical point of view, you'd be unlikely to hear this kind of sentence very often in practice. Except possibly in some kind of dispute where part of the sentence may be particularly stressed.
eg.maybe:
-it is an honour for us to have been invited
-Don't be silly! you don't mean that
-no,no, I insist . For us to have been invited is a huge honour.

Does it equalIs it equivalent to 'To have been invited to the party prompts in us an inordinate pride.' in meaning?

Yes, exactly, although there is also another type of for+to+infinitive clause which can't be so easily separated and which does fit well as the subject of the sentence

eg.
For 13 of our students to have been selected is a truly outstanding achievement.

For Boustany to have been found in breach of care by two Panels is pretty extraordinary under the circumstances.

Here the for + to is more like an infinitive-based that-clause. In fact it means pretty much the same thing as "that + should". ie. in the above sentences "For 13 of our students to have been selected..." and "For Boustany to have been found..." are close in meaning to "That 13 of our students should have been selected..." and "That Boustany should have been found...".

Originally Posted by Paperplane

Here the for + to is more like an infinitive-based that-clause. In fact it means pretty much the same thing as "that + should". ie. in the above sentences "For 13 of our students to have been selected..." and "For Boustany to have been found..." are close in meaning to "That 13 of our students should have been selected..." and "That Boustany should have been found...".

Paperplane, in "That 13 of our students should have been selected..." and "That Boustany should have been found...", is should used to express the importance of an action? For example like here:
It's important that somebody should talk to the police.
Is it necessary that my uncle should be informed?

Yes, exactly. In English should is sometimes used as a kind of pseudo-subjunctive(like in the examples you have given there). And so in the sentence "That Boustany should have been found..." 'should' conveys some kind of subjective attitude to what has occured. In this case perhaps among other things surprise.

Originally Posted by zxc

The subject of a sentence can never be within a prepositional phrase (in a 'for' clause).

Many thanks, zxc.