We must distinguish between the desirable and the prevalent practice. Under normal circumstances, it is at least desirable for people not to walk within four amot of someone in the midst of Shemoneh Esrei[1] (and perhaps Kri’at Shema[2] and Kaddish[3]). This is the simple reading of the gemara and the classical poskim and displays good middot. However, there are important poskim who provide a limud z’chut[4] for less than total fulfillment of the stated halacha. In some cases, stringency is unnecessary or undesirable. We will start with background.
There are two similar halachot regarding people who are near a person who is davening Shemoneh Esrei: not to sit within his four amot in any direction and not to pass in front of him.[5] The former’s main halachic concerns are sitting in a place where the Divine Presence (Shechina) is felt and/or appearing not to concur with the content of the davener’s tefilla. The entire issue of the latter halacha, of passing in front, is, according to almost all poskim, the fear of disturbing his concentration.[6] Since this issue is only that of affecting someone else, can he waive his rights? We agree with the column you cited, that one may not allow another to disturb his tefilla, just as he is not allowed to do anything to disrupt his own tefilla.
The poskim have displayed varied approaches regarding flexibility in borderline cases. The Shulchan Aruch[7] rules that one can pass near someone from the side, and the Mishna Berura[8] is inconclusive on the question of whether passing diagonally in front is a problem. He also entertains allowing leniency in specific circumstances where the problem is less severe (e.g., the davener has his face covered by a tallit), yet he stops short of permitting it outright.[9] The Aruch HaShulchan[10] is lenient where the two people are separated by furniture that is ten tefachim high (roughly waist high), whereas the Mishna Berura[11] is not. None of these sources, though, rationalizes walking directly in front of someone who is blocking access to the aisle.
Some bold ideas of limud z’chut for those who all but ignore the halacha are found in Eishel Avraham (Butchach)[12] and Tzitz Eliezer.[13] The former talks about making an optimistic assumption that, when he wants to pass, the davener has already finished the main part of Shemoneh Esrei or is taking a break in his tefilla. The latter even suggests that since so few people concentrate well anyway,[14] the halacha’s full force no longer applies. One should not follow these suggestions regularly but can use them to be tolerant of the lenient or in cases of special need.
When one needs to pass in order to fulfill a mitzva (e.g., a kohen has to duchen; he is the ba’al koreh) or he has an acute need to use the facilities, most poskim are lenient, as logic seems to dictate.[15] The Shulchan Aruch[16] says that the requirement to take the three steps back is insufficient justification to encroach on another’s four amot, even if the latter began davening late. However, when the davener’s actions create an unreasonable burden on others (especially, on a group) by blocking the door or aisle for an extended period of time, some poskim draw the line. Da’at Torah,[17] comparing this case to one who buries the dead in a public thoroughfare, says that it is permitted to traverse the area. Consider also that standing near the davener with an angry face may affect his concentration more than passing by. Of course, while a slow or late davener should give thought to his location’s effect on others, we should remember that he has feelings, too.