Hiya Chris,
I have photocopies of most of the Lochbroom P.R., I see a marriage 3 January, 1828 of "John McLeod Badintarbit and Ann McMichael Shinisgag".
Sionascaig one of the small settlements, mostly shepherds and a few servants, on the northern edge of Coigach, not surprising Ann was born in neighbouring Assynt. In the same file as Achnahaird, near the end (nother.htm), are a number of interrelated Michael familys. The surname still occurs in the area; Joan Michael at Ullapool writes the Column "Lochbroom Blethers" in the RossShire Journal.
John born Achnahaird may be tied to the family there at 41-3, and Achiltibuie 41-44, or not, livng at Badentarbat 1828 indicates either the family moved, or he did...
Badentarbat failed in 1842, most families removed to neighbouring farms, and the place becoming a sheep farm.
All the best,
Donald.