According to Barnes Commentary:
Which is a servant. Greek, "Who is a deaconess." It is clear, from the New Testament, that there was an order of women in the church known as deaconesses, Reference is made to a class of females whose duty it was to teach other females, and to take the general superintendence of that part of the church, in various places in the New Testament; and their existence is expressly affirmed in early ecclesiastical history. They appear to have been commonly aged and experienced widows, sustaining a fair reputation, and fitted to guide and instruct those who were young and inexperienced. Comp. #1Ti 5:3,9-11 Tit 2:4. The Apostolical Constitutions, Book iii., say, "Ordain a deaconess who is faithful and holy, for the ministries toward the women." Pliny, in his celebrated letter to Trajan, says, when speaking of the efforts which he made to obtain information respecting the opinions and practices of Christians, "I deemed it necessary to put two maid-servants who are called ministrae [that is, deaconesses] to the torture, in order to ascertain what is the truth." The reasons of their appointment among the Gentiles were these:
(1.) The females were usually separate from the men. They were kept secluded, for the most part, and not permitted to mingle in society with men, as is the custom now.
(2.) It became necessary, therefore, to appoint aged and experienced females to instruct the young, to visit the sick, to provide for them, and to perform for them the services which male deacons performed for the whole church. It is evident, however, that they were confined to these offices, and that they were never regarded as an order of ministers, or suffered to preach to congregations, #1Ti 2:12; #1Co 14:34.
According to editorial footnote on Calvin's Commentaries:
"Ministra," diakonov minister, or servant, or deaconess, one who ministers. Origen and Chrysostom considered her to be a deaconess, but the word does not necessarily prove this; for it is used often to designate generally one who does service and contributes to the help and assistance of others. She was evidently a person of wealth and influence, and was no doubt a great support and help to the Cenchrean Church. Those spoken of by Paul in #1Ti 5:10 and # Ti 2:3, were widows and aged, and they are not called ai diakonoi, deaconesses. There arose, as it appears, an order of this kind in the early Church, and Grotius says that they were ordained by imposition of hands before the Laodicean Council, which forbade the practice. Their office was, according to Bingham and Suicer, referred to by Schleusner, to baptize women, to teach female catechumens, to visit the sick, and to perform other inferior offices in the Church. But this was the state of things after the apostolic times, and there is no reason to believe that Phoebe was of this order. She was evidently a great helper of the Christian cause, as some other women also are mentioned in this chapter, and she had been the helper of many, (# Ro 16:2,), and not of one Church, and also of Paul himself; and from what is said in # Ro 16:2, it appears probable that she was a woman carrying on some business or traffic, and that she went to Rome partly at least on this account. Ed.
According to Jamieson, Fausset, and Brown's Commentary:
That in the earliest churches there were deaconesses, to attend to the wants of the female members, there is no good reason to doubt. So early at least as the reign of Trajan, we learn from PLINYS celebrated letter to that emperorA.D. 110, or 111that they existed in the Eastern churches. Indeed, from the relation in which the sexes then stood to each other, something of this sort would seem to have been a necessity. Modern attempts, however, to revive this office have seldom found favor; either from the altered state of society, or the abuse of the office, or both.
According to Matthew Henry's Commentary:
As a servant to the church at Cenchrea: diakonon, a servant by office, a stated servant, not to preach the word (that was forbidden to women), but in acts of charity and hospitality. Some think she was one of the widows that ministered to the sick and were taken into the churchs number, #1Ti 5:9.
According to Robertson's NT Word Pictures:
Who is a servant of the church (ousan diakonon thv ekklhsiav). The etymology of diakonov we have had repeatedly. The only question here is whether it is used in a general sense or in a technical sense as in # Php 1:1; #1Ti 3:8-13. In favour of the technical sense of "deacon" or "deaconess" is the addition of "thv ekklhsiav" (of the church). In some sense Phoebe was a servant or minister of the church in Cenchreae. Besides, right in the midst of the discussion in #1Ti 3:8-13 Paul has a discussion of gunaikav (verse #11) either as women as deaconesses or as the wives of deacons (less likely though possible). The Apostolic Constitutions has numerous allusions to deaconesses. The strict separation of the sexes made something like deaconesses necessary for baptism, visiting the women, etc. Cenchreae, as the eastern port of Corinth, called for much service of this kind. Whether the deaconesses were a separate organization on a par with the deacons we do not know nor whether they were the widows alluded to in #1Ti 5:9.
Seems to me that the preponderance of historical evidence indicates that women WERE officially appointed as servants in the Christian congregation, even if their specific responsibilities differed somewhat from the male diakonoi.
Craig