Learning Torah on Subways II

In a comment to this post, Rabbanit Chana Henkin offered readers a copy of R. Yehuda Henkin's article "Contemporary Tzeni'ut" from Tradition 37:3 (Fall 2003). I had forgotten that he addresses this issue in that article. Here is a relevant excerpt (pp. 5-6):

Shema is paradigmatic of all prayers and blessings: none may be recited in the presence of uncovered erva [nakedness] of even rabbinical nature. Is studying Torah permitted in such circumstances? Sefer Yere'im forbids it, and for that reason relies on "et la'asot la-Shem" [emergency negation of the law] for a dispensation to permit Torah study within earshot of the songs of gentile women; he is cited by a number of Rishonim. All the more so, this would apply to tefah [a handbreadth of uncovered nakedness].

However, others disagree. Me'iri writes in Berakhot 24a:

Seeing a tefah in his wife anywhere that is normally not exposed, prohibits Keri'at Shema but does not prohibit divrei Torah, since seeing causes hirhur.

This is also the opinion of sefer ha-Hashlama...

This is important support for permitting men to lecture on Torah and mussar to audiences that include women who are improperly dressed.