When one commits to learning mishnayos l’iluyi neshama, is he giving away his own schar for the mitzva of talmud torah to the niftar
If not, then how does it work exactly?
Dedicating a learning session for iluy neshamah does not imply that the person himself does not receive the reward of the Torah learning. However, the extra learning itself, which would otherwise not have been achieved, is an iluy for the soul of the deceased. The deceased receives the sechar of the learning session, which was initiated because of him, but the actual sechar of Torah study belongs to the person who studies the Torah. This is my understanding of the matter, though I have not found sources.
After some searching, I saw the following in Derech Sichah (anectdotes and questions & answers from Hagaon R’ Chaim Kanievsky), on p. 484:
Q: After the Ponevizer Rav was niftar, the mashgiach (Rav Yechezkel Levenstein) accepted upon himself to “break one character trait” for the iluy neshamah of the Rav. Does this help?
A: And how does learning for iluy neshamah help — can the sechar of learning be given away? Rather, the sechar of the niftar is that the person who learns is awakened to learn Torah through the niftar, which grants him sechar — but if he was awakened to study Torah without connection to the niftar, the niftar has no gain from it.
The questioner noted that Rav Yechezkel Levenstein would probably have “broken the character trait” without connection to the petirah of the Rav, at which Harav Kanievsky smiled.
In another response, Harav Kanievsky added that when a son learns Torah it causes an iluy neshamah for the father even when the learning was not initiated on his account.