Sentence: It mightn't strike you as at all funny but then if it doesn't,...

[Bhikkhu1991a]

Hello Alan Townend,

Could you please explain what are the definitions of the following underlined “it” in bold? What are their antecedents, for example?

Here are the excerpts from the Newsletter “A bit of a laugh” dated November 14, 2008:

1. It mightn't strike you as at all funny but then if it doesn't, at least I shall be spared the embarrassment of you not reacting at all. (Paragraph 1, line 4)
2. Let me tell you a bit more about 'a bit of a laugh'. It's the sort of expression we use to describe something you do in a light-hearted way. (Paragraph 3, line 2)
3. to visit the local casino to try to win some money. It's the sort of thing you do once in a while, not very often. (Paragraph 3, line 6)
4. Of course you can laugh so much that you simply can't stop. You know what it's like, it's catching. (Paragraph 4, line 2)
5. You want to laugh but you can't and so you keep it to yourself and laugh up your sleeve — I should imagine if you tried doing this, it could be very awkward! (Paragraph 4, line
6. Mind you, it could be that you and the others get jobs somewhere else for much more money and then it's the turn of the boss to laugh on the other side of his face. And of course nowadays getting a job is important and it's a very serious business if you can't get one or you lose your present job. (Paragraph 4, line 12)
7. who said to themselves:' No problem I'm very good at making the girls laugh — it'll be a piece of cake'. (Paragraph 8, line 3)
8. So I hope you've had a lot of laughs — maybe it was the first time you had a LOL. ( The paragraph below Alan Townend, line 1)

According to Oxford Advanced Learner’s Dictionary (7th Edition), there is long list of definitions for “it”, unfortunately, I don’t’ know the following “it” belonged to which definitions. Further, the dictionary is protected by copyright, so the list of definitions cannot be provided here.
I hope to hear from you soon. Thank you so much.

Best wishes.