SDO treats the issue of deacons within religious orders. I confess my own ignorance on this practice. Is it widespread at all? The liturgical and teaching role within a community is clear enough. Many orders practice an apostolate in line with how the deacon is asked to serve. How often are religious permanent deacons necessary?
32. The institution of the permanent diaconate among the Religious is a right reserved to the Holy See which is exclusively competent to examine and approve the recommendations of the general chapters in the matter.
33. Let the Religious deacons exercise the diaconal ministry under the authority of the bishop and of their own superiors according to the norms in force for religious priests; they are also bound by the laws to which the members of the same Religious family are obliged.
34. A Religious deacon who lives either permanently or for a specified time in a region which lacks a permanent diaconate may not exercise diaconal functions except with the consent of the local Ordinary.
35. The provisions in nos. 32-34 regarding the Religious must be regarded as applying likewise to members of other institutes who profess the evangelical counsels.[Canon Law of the Eastern Church, <Concerning Persons> canon 87, AAS 49 (1957) p. 462.]