Fonia / Fionnghuala of Moray, Lady of the Isles - Moved up a generation

This seems to assign too much importance to general guesses about the dates.

William fitz Duncan was born, say 1090. His son Donald was born, say 1135 but could be a decade or even two decades earlier. Fiona was having children say 1170. Her age is a guess.

So, is she one or two generations down from William?

I don't think the information we have supports categorical statements like "Her dates do not support ..."

Her dates *as given in her profile* made her fit better under William FitzDuncan his ownself, and he *did* have a reputation as a "tireless tomcat" (Bishop Wimund could very easily have been another of his wild oats).

We do have approximate dates for Raghnall mac Somairle - but no confirmation that he was married to this Fionnghuala person. ("Fiona", by the way, is relatively modern - I think it may have been Sir Walter Scott who came up with is, as he did "Cedric" by an accidental transposition.)

Here's where all that apparently comes from: Domhnall was, reputedly, the son of Raghnall (fl. 1192) son of Somhairle (died 1164). The 17th-century History of the Macdonalds by Hugh MacDonald of Sleat claimed that Domhnall's father Raghnall had married a daughter or sister of the early 14th-century hero Thomas Randolph, Earl of Moray. Sellar suggested that this tradition may have derived from a garbled version of reality. Perhaps, Sellar argued, his mother was a daughter of William fitz Duncan. The latter was another famous Earl of Moray, but one who lived in the 12th- rather than the 14th-century.[1]

In a charter to Paisley Abbey Domhnall's father Raghnall is given a wife named Fonia (Fionnghuala?),[2] though there is no direct proof that this was the name of Domhnall's mother. Domhnall's father Raghnall, carrying the legacy of his own father Somhairle, was a powerful Argyll and Hebridean magnate who, depending on context, bore the titles "King of the Isles", "Lord of Argyll and Kintyre", and "lord of the Hebrides (Inchegal).[3] His father's legacy was such that he became the ancestor figure of both Clan Ruaidhri and Clan Donald.[3] (Wikipedia)

Source:
1) Sellar, "Hebridean Sea-Kings", p. 200.
2) Sellar, "Hebridean Sea-Kings", p. 195; McLeod & Bateman, Duanaire na Sracaire, p. 503 states, without citing evidence, that this woman was a grand-daughter of Fergus, King of Galloway.
3) a b Sellar, "Hebridean Sea-Kings", p. 194, table ii.

Derivation of "Fiona" (as pronounced "Fee-OH-na") is earlier than I thought:

Fiona is a feminine given name. The name Fiona was invented, and first used, by the Scottish poet James Macpherson (1736–96), author of the Ossian poems, which he claimed were translations from ancient Gaelic sources (sources, when challenged, he never produced). The name was subsequently used as a pseudonym by William Sharp (1855–1905), who authored several romantic works under the name "Fiona Macleod". The name has since become popular in England, Scotland and Ireland. https://en.wikipedia.org/wiki/Fiona

As written with an accent over the "i" and pronounced "FEE-o-na" or "FEE-neh", it *may* be period - the spelling "Fíne" is much more common. (O Corrain & Maguire, Irish Names)

Much better. It's not the particular conclusion I object to, it's the Rambo-style approach to changing information without good supporting arguments.