Responsa for Bava Batra 114:6
א"ר יוחנן משום ר' בנאה בכל שותפין מעכבין זה את זה חוץ מן הכביסה שאין דרכן של בנות ישראל להתבזות על הכביסה
and [commenting on this] R. Hiyya b. Abba said: This refers to a man who does not look at the women when they are washing [clothes]. How are we to understand this? If there is another road, then if [he does not take it] he is wicked.<span class="x" onmousemove="('comment',' Because it is a duty to keep away from temptation. ');"><sup>11</sup></span> If there is no other road, then how can he help himself? — We suppose that there is no other road, and even so it is incumbent on him to hide his eyes from them.<span class="x" onmousemove="('comment',' Lit., 'to constrain himself'. ');"><sup>12</sup></span>
Teshuvot HaRivash
Also, regarding your suggestion that some of the people without seats could put portable seats in the middle of the synagogue and sit there, or sit on rows of clean mats on the ground if they wish, for no individual owns anything other than his space and its entrance and exit access, but everyone owns the rest equally: They also may not do this. For even those who own seats, with access for entrance and exit, may not use that which is a path belonging to others ... just as residents of a street or [shared] yard may not use the street or yard other than in ways that residents normally use streets or yards ...
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