- He was pretty emphatic about me leaving.
- He was pretty emphatic about my leaving.
Which is correct, and why?
A purist would say: His emphasis was about an act of leaving. What act of leaving? My act. Therefore, my leaving.
But “me leaving” is also very common, and can (at least sometimes) be defended by an alternate analysis: He was emphatic about me, and the leaving modifies me. Then it must be a participle, rather than a gerund as in my first version.
[1] He was pretty emphatic about [me leaving].
[2] He was pretty emphatic about [my leaving].
They are both correct and have the same meaning. "My leaving" and "me leaving" are both subordinate participial clauses with "my/me" as subject and "leaving" as the predicate verb phrase.
The only difference is that genitive "my" is more formal than accusative "me".