From the Congregation for Divine Worship (Protocol No. 930/08/L), dated November 22, 2008, and signed by Fr Anthony Ward, SM, Under-secretary of the Congregation stated the following:
1. The liturgical blessing of the Holy Mass is properly given to each and to all at the conclusion of the Mass, just a few moments subsequent to the distribution of Holy Communion.
2. Lay people, within the context of Holy Mass, are unable to confer blessings. These blessings, rather, are the competence of the priest (cf. Ecclesia de Mysterio, Notitiae 34 (15 Aug. ‘97), art. 6, §2; Canon 1169, § 2; and Roman Ritual De Benedictionibus (1985), n. 18).
3. Furthermore, the laying on of a hand or hands — which has its own sacramental significance, inappropriate here — by those distributing Holy Communion, in substitution for its reception, is to be explicitly discouraged.
4. The Apostolic Exhortation Familiaris Consortio n. 84, “forbids any pastor, for whatever reason or pretext even of a pastoral nature, to perform ceremonies of any kind for divorced people who remarry”. To be feared is that any form of blessing in substitution for communion would give the impression that the divorced and remarried have been returned, in some sense, to the status of Catholics in good standing.
5. In a similar way, for others who are not to be admitted to Holy Communion in accord with the norm of law, the Church’s discipline has already made clear that they should not approach Holy Communion nor receive a blessing. This would include non-Catholics and those envisaged in can. 915 (i.e., those under the penalty of excommunication or interdict, and others who obstinately persist in manifest grave sin)”.
So it would seem clear that the giving of blessings at Communion time to anyone, for any reason is not permissible. This is not a matter of personal preference, but of obedience to Holy Church. What seems strange is that no-one seems to know of this - and many other rulings - that come from the various Roman Congregations. So much comes from the diocesan offices for this and that at a local level but documents from Rome (on topics great and small) seem to get very little publicity.
A great many little habits seem to be accruing to the liturgy in these days: "something nice I saw at a Methodist service", "a lovely thing we did at children's camp". I even know somewhere that is still doing that 1970's thing of bringing up stones to the altar during Lent to represent our sins - all so very nice if you like that sort of thing but, please, not inserted into the Mass! (We have a perfectly good, Church-mandated and biblically based symbol for sin in Lent - the imposition of ashes).
The Second Vatican Council's Constitution on the Sacred Liturgy, Sacrosanctum concilium, aimed to 'reform' the sacred Mysteries by removing 'unnecessary repetition' and 'accretions' - lamenting "the intrusion of anything out of harmony with the inner nature of the liturgy" (SC 21).
Fr. Joseph Jungmann (The Mass of the Roman Rite, 3 vols., Christian Classics, 1950, 1986), shows that from the time of the earliest known Roman sacramentaries (5th and 6th century) the Roman Rite had absorbed customs from other local Churches (e.g. Gaul), as well as developed it's own, an evolution that ended with Pius V and Trent. What had once been "novelties" when first adopted at Rome became fixed parts of the "immemorial Mass". The only constant being the authority of the Apostolic See to permit, order and even to impose them or abolish them.
Priests (well, at least me) are often faced with the claim that “these things happen at other Churches”. Our reply must be that such things should be addressed to the competent authorities, since no-one "even if he be a priest, may add, remove, or change anything in the liturgy on his own authority". (SC 22.3). Would that such things were more widely publicised by our diocesan liturgy offices. (Month by month I scour their literature for a chant workshop or how to offer Mass in the Extraordinary Form - hope springs eternal). Doesn't it say somewhere that every priest is responsible for the Sacred Liturgy in his Parish which he is“bound to watch over so that no abuses creep in” - yes it does, Canon 528 §2.