[1] In 1801, the 12th Earl of Eglinton, Hugh Montgomerie, persuaded Dr MacKenzie to move from Mauchline to Irvine and live free of rent for life at Seagate House.

But afterwards, when the conversation, which was on a medical subject, had taken the turn he wished, he began to engage in it, displaying a dexterity of reasoning, an ingenuity of reflection, and a familiarity with topics apparently beyond his reach, by which his visitor was no less gratified than astonished."

[1] In 1786 MacKenzie received a rhymed summons from Burns to attend: "a procession celebrating the Festival of the Nativity of the Baptist, Friday first's the day appointed".

In "The Holy Fair", Dr MacKenzie is personified as "Commonsense", who left the assembly to keep a dinner appointment with Sir John Whiteford at the home of the Earl of Dumfries as soon as "Peebles, frae the water-fit" began to preach.

Findlay states that in September 1786 "John MacKenzie, happening to call at Gavin Hamilton's house at the time that Burns was reading his performance (of 'The Calf'), was so tickled with the verses that he extracted from him the promise of a copy, which he sent the same Sunday night, accompanied by a brief note, telling him that the fourth and last stanzas were added since he saw him that day".

[10][1] MacKenzie sent off letters of recommendation to Sir John Whitefoord and to the Honourable Andrew Erskine in preparation for Burns visit to Edinburgh.

[11] The earliest account of the distressing affair regarding David McLure and the litigation against Robert Burns's father was given by Dr MacKenzie who said that he had attended William Burns at Lochlea towards the end of his life and from him received "a detail of the various causes that had gradually led to the embarrassment of his affairs; these he detailed in such earnest language, and in so simple, candid, and pathetic a manner as to excite both my astonishment and sympathy".

[12] In 1827, the year of his retirement, he presided at the opening dinner on 25 January of the Irvine Burns Club, with the well-known Mr. David Sillar, "a brither poet" (Epistle to Davie), as vice-chairman.