Confirmation of illegitimacy

[arthurk]

For information MacGrigor because it will most probably come up again, the calendar changed in 1750

https://en.wikipedia.org/wiki/Calendar_(New_Style)_Act_1750

The Act was dated 1750, but the change actually took place in 1752.

So was he christened before his parents’ marriage or not?

You'd need to view the original register or bishop's transcript to know for sure. Some people transcribing registers put down the year exactly as they find it (ie Old Style), and some convert it to New Style. And not everyone makes it clear which method they've used.

EDIT:
Sorry - I missed the bit where you mentioned 1709/10. That means 1709 Old Style and 1710 New Style, and, if used correctly, is unambiguous.

What’s M.I.?

In this context, probably a Memorial Inscription. (In FHS contexts it can also be Members' Interests. FHS = Family History Society.)

[MacGrigor]

Thanks for all of that!