"Never will I forget seeing him stand on the deserted station platform."
Why is the word "stand" is in its infinitive(?) form? Isn't it supposed to be "stands" since the subject here is "him"?
Verbs of perception like see, hear, listen, watch, feel are often followed by +obj pronoun+ either a base form infinitive or a gerund.
I saw him standing in the rain.
I heard the bell ring once.
I could feel her raging inside while I was telling her the truth.
The use of the gerund or the base form infinitive is a different matter. It basically depends on the speaker's perception of the action that's being referred to and on its context.
Hope it helps.
We tend to use the bare infinitive when we perceive the complete action, the -ing form when perceive part of the action:
I saw him walk across the road.
I heard him say good morning to his neighbour
I saw him walking down the street.
I heard him talking to his neighbour over the fence.
Context is always important; labelling is rarely important.
CAUTION: NOT A TEACHER
(1) May I just add a point to the excellent answers that you have received?
(2) Yes, you are 100% correct: most books would agree with you that "him" is the
subject. BUT the problem is that it is the subject of the bare infinitive "stand."
(a) You know from your studies that if you want to use "stands," you need to
use the form "He." I am sure that you would NEVER say
"Him lives in Paris" instead of "He lives in Paris."