Sentiment and irony

In his poem 'The Definition of Love', Bernard O'Donoghue suggests love is not what has previously been suggested (not sex, not wishing someone else's welfare), but is rather fingers touching fingers across a linen tablecloth. The last nine lines of the poem are given over to this little narrative:

A young curate of a parish in West Cork
Was told his mother was seriously ill
And he must come home to Boherbue
(In fact she was dead already; they had meant
To soften the blow). He drove recklessly
Through mid-Kerry and crashed to his death
In the beautiful valley of Glenflesk.
This was because he fantasised in vain
About touching her fingers one last time.

Beautifully handled, this: the use of plain language and the plain measure of blank verse, the vocabulary titivated by the expressive use of Irish place names; the way the syllabic count contracts (11, 10, 9; and then again 11, 10, 9) until the punctus is reached at 'death', whereafter the lines are all regularly decasyllabic. It is properly touching poetry. More, its the kind of dramatic irony (as in Greene's Heart of the Matter) that is both surprisingly resonant and surprisingly rare in contemporary literature. Why should this be? I've been thinking about it, and I wonder if my first reaction -- that it is too sentimental for modern tastes (although 'sensibility' is not a criterion of aesthetic dispraise, in my book) -- hasn't got it the wrong way about. What I mean is I wonder now whether the definition of sentimentality isn't, as it is often taken to be, grounded in affective response; whether sentimentality isn't more radically the iteration of a certain sort of dramatic irony.