An update: after a serious canter around Minutes from several Presbyteries and Kirk Sessions in Banffshire and Orkney, Strathbogie Presbytery Minutes 7-3-1733 (pg 241 CH2/342/5) has this "Mr Alexander Geddes Student in Divinity now in Keith Parish...". Alexander Geddes h/o Janet Cuie was in Nether Clune in Deskford before and after this date, so that settles it: the Probationer who preached at Deskford and the Schoolmaster who messed up his Deskford Kirk Session Minutes are two different people.
I'm interested in the Schoolmaster rather than the Probationer, so I can put the latter to my MiscRef files, tentatively assigned as son of George Geddes & Margaret Innes of Kempcairn, Keith (thus born late 1709 which I still think is too young to have graduated in 1727, at only age 17).
But a big skeleton fell out the cupboard. Our Birsay Alexander Geddes was accused of Jugling (look it up!), Disenginuity, Breach of Promise and Indecent Behaviour. His ordination had to be delayed because it was objected to; and the alledging Presbytery of Kirkwall clashed with the neighbouring Cairston Presbytery which Birsay parish is in. The latter defended him to the hilt; the former was severely put out and got cuttingly pompous in the criticism of their so-called affectionate brethren down the road; and I think the Synod got involved. Maybe Orcadians know all about this Island-wide scandal of the 1730s. And I do now...
These Minutes, all now freely available of course, can be a goldmine if one can take the time to wade through them.