My question is, the Gemara describes as one of the disparaged categories, "one who has relations when he is excommunicated". Didn't we learn earlier (or perhaps in Kesuvos) that there is no problem with relations with a wife when excommunicated because of the principle of "eishto kegufo", one's wife is like one's own person?
Barry Shain, New York, United States
It is true that the ROSH on our Gemara mentions that it is prohibited to have relations with one's wife while excommunicated. However, whether or not it is permitted is actually the subject of a query in the Gemara in Moed Katan 15b. The Gemara leaves the question unanswered, and the l'Halachah we are lenient because of Safek d'Rabanan l'Hakel (RIF, Be'er Hetev YD 334:8). Perhaps the Rosh here does not mean they are literally prohibited to have Tashmish, but that it should be avoided (as is the case with the rest of the "9 Midos"). Alternatively, he may have argued with the Rif and ruled stringently regarding Tashmish based on our Gemara.
The discussion of "Ishto k'Gufo" that you remember might be from the RAN, beginning of 8a, in the name of the RA'AVAD. They do not discuss Tashmish, but rather coming within four Amos of a wife/husband that is Menudah. The Ra'avad proves that it is permitted for the wife to approach within four Amos of a husband who is Menudah, since otherwise how could the Gemara discuss whether Tashmish is permitted!
We may wonder, as you asked, why Ishto k'Gufo does not permit Tashmish as well. The answer to this question is rather straightforward:
There is a clear distinction between the two Halachos. Distancing one's self four Amos from the Menudah is a Halachah that applies to all people in the world besides the Menudah himself, obviously. Since it does not apply to him, it does not apply to his wife either. However, the Isur of Tashmish is an Isur that does apply to the Menudah (since he is like an Avel). Ishto k'Gufo, then, will not permit his wife to have Tashmish with him.