It is not appropriate to the liturgical action, because it interrupts the words being said. Which are the words of a hymn of praise:
St. Luke 2:
2:8 et pastores erant in regione eadem vigilantes et
custodientes vigilias noctis supra gregem suum
2:9 et ecce angelus Domini stetit iuxta illos et claritas Dei
circumfulsit illos et timuerunt timore magno
2:10 et dixit illis angelus nolite timere ecce enim evangelizo
vobis gaudium magnum quod erit omni populo
2:11 quia natus est vobis hodie salvator qui est Christus
Dominus in civitate David
2:12 et hoc vobis signum invenietis infantem pannis involutum et
positum in praesepio
2:13 et subito facta est cum angelo multitudo militiae caelestis
laudantium Deum et dicentium
2:14
gloria in altissimis
Deo et in terra pax in hominibus bonae
voluntatis
2:15 et factum est ut discesserunt ab eis angeli in caelum
pastores loquebantur ad invicem transeamus usque Bethleem et
videamus hoc verbum quod factum est quod fecit Dominus et
ostendit nobis
2:16 et venerunt festinantes et invenerunt Mariam et Ioseph et
infantem positum in praesepio
2:17 videntes autem cognoverunt de verbo quod dictum erat illis
de puero hoc
2:18 et omnes qui audierunt mirati sunt et de his quae dicta
erant a pastoribus ad ipsos
2:19 Maria autem conservabat omnia verba haec conferens in corde
suo
theworld.com/obi/Religion/Vulgate/Luke.txt
If people wish to clap, they should go elsewhere.
The problem with it is, that if behaviour more appropriate to our life outside the liturgy is imported into it on no very clear principle, the distinctive character of the liturgy as an act of Christian worship will be lost, & the liturgy will seem to be no more significant than any other permissible form of behaviour, such as watching TV or eating sweets.
It is a terrible idea. it opens the way to the complete loss of our sense of the “otherness” of God, the God Who is to be approached with holy awe & reverence. So although God is also intimately concerned in every instant of the lives of each one of us, it is illegitimate to reason from the appropriateness of eating sweets or clapping hands or watching the box outside the Liturgy, to the appropriateness of doing these things during it. Nobody would suggest that eating sweets or sleeping, or drinking beer, is appropriate during a wedding Mass; so why is it appropriate to clap hands during the Sunday Liturgy, which is a Commemoration both of the Passion & of the Resurrection ?
Besides, as the public worship of the entire Church on earth, the Liturgy is supposed to be offered to God in certain ways rather than in others; which is why there are rules for it - otherwise it risks becoming an anarchic free-for-all, in which people “do what is right in their own eyes” - always a bad thing in the Bible. But “God is not a god of confusion”.
This failure to understand the character of the Liturgy only leads to trivialisation of it - I blame the assumption that the Liturgy is “our” action: that is part of the truth, but, it is ours, only because it is primarily, & in every way, God’s. It is an enormous privilege to share in the Liturgy, for by so doing, mortal, sinful men are made sharers in the Priestly activity of Christ. ##