Ethically, should an observant (traditional or trthodox) Jewish man attend a shiva minyan when it is not known if there will be a mechitzah (divider separating the genders during prayers)? If there isn't one, can he still attend & be counted, even if he doesn't daven (pray)?

HaRav Moshe Feinstein, of blessed Memory, was considered  the Halachic arbiter of Orthodox synagogue guidelines.  In a posthumous publication of his responsa, the following is reported.

 

Rav Moshe was concerned with whether it was necessary to have a Mechitzah separating the men and women sections for prayer, in the event that there were only one or two women. He notes: "Throughout the generations the common custom was for a poor woman to be in the Bet haMidrash to receive charity, or as a mourner to recite Kaddish." His response was that a Mechitzah was necessary even for one woman [who attended] on a regular basis. On an occasional basis, it was not necessary, should only one or two women be present. (Igerot Moshe, Vol. 8, Orech Chayyim 5:12b)

 

Note the terminology and the concern. Rav Moshe does not question the propriety of the woman who comes to the Bet haMidrash to recite Kaddish. He seems to assume that there are no Halachic qualms at all with such a function of women at religious services.

 

The only problem is whether there needs be a Mechitzah during her recital. Indeed, it is apparent that Rav Moshe accepts a woman reciting Kaddish as a normal, unquestionable practice.

 

In addition,there seems to be a leniency in that for a few women a Mechitzah is not necessary on an occasional basis. A “shiva House”is definitely an occasional situation. As such, at a Shiva minyon it would be permitted for an Orthodox person to attend even without a Mechitzah, providing there are only a few women.

 

 

 

For an  Orthodox Jew participating in a Shiva minyan without a mechitzah constitutes a violation of halacha to which he is committed and therefore he cannot attend the Shiva minyan.  This does not relieve him of the obligation to comfort the mourner and he should make a visit during Shiva. If his merely being present allows him to be counted in the minyan and does not constitute a violation of the halacha it would be the ethical thing to do. It is important to understand that those who are committed to an halachic way of life have no choice but to follow the halacha. Those who are not committed to the halacha should try to understand that this may mean that sometimes a person cannot do something that would seem appropriate to those who are not halachically observant.