If I understand your tortured prose, you're saying Aquinas makes no distinction between formal and material heresy, correct?
That's not true.
Accordingly, in the first way the Church does not forbid the faithful to communicate with unbelievers, who have not in any way received the Christian faith, viz. with pagans and Jews, because she has not the right to exercise spiritual judgment over them, but only temporal judgment, in the case when, while dwelling among Christians they are guilty of some misdemeanor, and are condemned by the faithful to some temporal punishment. On the other hand, in this way, i.e. as a punishment, the Church forbids the faithful to communicate with those unbelievers who have forsaken the faith they once received, either by corrupting the faith, as heretics, or by entirely renouncing the faith, as apostates, because the Church pronounces sentence of excommunication on both.
"Forsaking the faith once received" is formal heresy. In fact, most discussions of heresy in the pre-Reformation Church relate to formal heresy.
Obviously RC posters here either do not see as binding the church teaching which Aquinas refers to, or subsequently, which forbids RCs to communicate with heretics who have forsaken the faith they once received, or they do not see those like myself, former weekly RCs, as guilty of the heresy which excludes such from religious engagement with, and presently damned.
Or they may be unaware of Aquinas' writing on the matter or they may be unaware that the person with whom they are conversing is a formal heretic. Or they may consider that "punishment" of the heretic (one of Aquinas' two reasons for proscribing communication) may result in further alienation rather than reconciliation, which I'm sure Aquinas would agree, is undesirable.
It's worth noting those two conditions of Aquinas:
I answer that, Communication with a particular person is forbidden to the faithful, in two ways: first, as a punishment of the person with whom they are forbidden to communicate; secondly, for the safety of those who are forbidden to communicate with others.
In the case of this forum, the second condition is largely not applicable. As Aquinas himself goes on to say:
With regard to the second way, it seems that one ought to distinguish according to the various conditions of persons, circumstances and time. For some are firm in the faith; and so it is to be hoped that their communicating with unbelievers will lead to the conversion of the latter rather than to the aversion of the faithful from the faith.
I think it's in this spirit that communication occurs.
What i said was that it was not spelled out, not that is could not be derived by interpretation.
"Forsaking the faith once received" is formal heresy.
And what it can mean and who has forsaken the faith they once received is interpretive. You have bishops judging liberal RC pols as members, and the pope cordially thanking a manifestly impenitent Teddy K for his prayers, and with the the closest thing we can see to a rebuke being that of a giving him an "apostolic blessing," while giving him a church funeral, which canon law forbids for notorious public sinners, thus Rome apparently did not judge such as being one who departed from the faith. Or does that mean he would have had to leave Rome and perhaps become a conservative evangelical? No doubt then real concern for his soul would be manifest.
Or they may be unaware of..or they may be unaware...Or they may consider ... it is to be hoped that their communicating with unbelievers will lead to the conversion of the latter rather than to the aversion of the faithful from the faith.
So that must be what allows you to converse with such as me, despite what some past teaching said, but the point here is that we see variant interpretations on this matter, while you make made the teaching of Dr. Aquinas determinative on this matter, and thus perhaps we should expect you to affirm something else he said on this subject:
"On the other hand, there are unbelievers who at some time have accepted the faith, and professed it, such as heretics and all apostates: such should be submitted even to bodily compulsion, that they may fulfil what they have promised, and hold what they, at one time, received". — Living Tradition, Organ of the Roman Theological Forum, http://www.rtforum.org/lt/lt119.html
And at one time obedience to the pope required exterminating all the heretics from the land, akin to Islam, and now they professes to worship the same god, while some RCs here consider Prots as myself to be lost, while their church makes them brethren with liberals. Its quite an amalgamation.