(At the end of the 2nd full para, last page of Insights) Rabah said (Bava Metzia (86a) "I am a Hachid (peerless) in the study of Nega'im, and I am Yachid in the study of Ohalos." My question is, is this kind of declaration not contrary to the modest response when one is asked if he learned mesechas so and so, "No, I did not learn it."? I am sure there must be some special dispensation here, but I am wondering just how and to who Rabbah made the seemingly boastful statement to begin with.
With best wishes to all.
The Gemara in Bava Metzia (23b) which you mention, that a Talmid Chacham should say "no" when he is asked whether he has a learned a certain Masechta, is referring to when the questioner simply wants to know how much this Talmid Chacham has learned (as Tosfos says), and has no practical motive in asking him (for example, he has a question in the Masechta which he needs answered). Rabah, though, was informing his colleagues that he was qualified to answer their questions in two of the most difficult areas of Torah, and he was making his services, so to speak, available to them.
Alternatively, the Gemara in Nedarim (62a) cites the verse, "A stranger shall praise you, and not your own mouth," and explains that this does not apply in a place where the people do not recognize you; in such a place, it is permitted, and advised, to inform the people that you are a Talmid Chacham, or a G-d-fearing person (Yerei Shamayim). The Zohar (Bamidbar 193b; see also Maharsha in Nedarim) derives this from the verse itself by reading the verse as follows, "A stranger shall praise you, and [if] not, [then] your own mouth [should praise yourself]."
Be well,
-Mordecai