This blog commenter is new to me, and, I suspect, to many.
It is not uncommon for talmidim to write semi-anonymously under the name of a famous person from the past (though at the moment, the only one that springs to mind is Rabban Gamliel (blog here: http://rabbangamliel.blogspot.com/), who as you may have guessed is probably not the well-known tanna.
The name Ibn Ya'ish in a talmidish context is of Andaluthian origin. One of the more well-known bearers of this nasab was Baruch ben Isaac Ibn-Ya’ish, exact dates unknown to the internet, fifteenth century philosopher, medical scholar, and translator from Spain who settled in Italy.
A commentary on canticles, ecclesiastes, and proverbs entitled 'Mekor Baruch' was also from the hand of Baruch ben Isaac Ibn Ya’ish, though it is unclear on the internet whether this is the same Ibn Ya’ish. The author was from Cordoba, and may have been Yahi’a Ibn Ya’ish, the first Chief Rabbi of Portugal, who was born in the 12th century.
[This Mekor Baruch ('source of brocha') is not to be confused with the Mekor Baruch written by Rav Baruch ben Yisroel Hager of Vishnicz (1895 - 1963, Seret-Vishnitz chassidic dynasty), who shtams af from Ya'akov Koppul, disciple of the Ba'al Shem Tov. Nor is it the Mekor Baruch written by Rav Baruch HaLevi Epstein mi Pinsk (1860 - 1941).]
Concerning the name Ibn Ya’ish, it should be mentioned that this was a notable Jewish family of Babylonian origin, being descendants of Reish-galuso Hezkiyahu, and thus also descendent from King David (and so alledgedly relatives of the mediaeval dukes of Brabant, but this is by no means certain).
[The name Ibn Ya'ish means 'son of the one that lives'; ibn means 'son' or 'son of', ya'ish means 'he lives'. It is a patronymic or descent-group nomen, rather than an ism (name) or laqab (descriptive of a characteristic or a place-attribution).]
After the expulsions, many members of the Ibn Ya'ish family ended up in the Ottoman Empire.
Among them: Rabbi Avraham Ibn Ya'ish, died in 1554; and Don Solomon Abenaes (Ibn Ya'ish), who was also named Alvaro Mendes (born 1520 in Portugal, died 1603 in Turkey. He may have been the brother of David ben Avraham Ibn Ya'ish.
So, the Ibn Ya'ish referenced in the name of the commenter on MarGavriel's blog is NOT the Islamic scholar Muhammad Ibn Ya’ish who wrote ‘Madrasat Al Imam 'Umar Ibn 'Abd Al Barr’ (School of Imam Omar ibn Abd el Barr – about the contribution of Imam Omar ibn Abdelbarri the Andalusian and his followers on the development of the Maliki school of Sunni Islamic jurisprudence), nor the mediaeval Ibn Ya’ish who wrote a commentary on the Kitab al Mufassal (book of elaboration – a treatise on grammar by Abulkassim Mahmud ibn Umar ez-Zamakhshari, also known as Jarullah).
Nor is it in reference to Ubayd Ibn Ya'ish, whom Al-Khatib quoted as saying "thirty years I did not eat from my own hand - my sister fed me while I wrote Hadith".
But it may be some other Ibn Ya'ish after whom our pseudonymous commenter has called himself.
In which case all of this post is of no help whatsoever.