When asking how to deal with rejection letters, it seems to vary a lot how people deal with them. Some say you should be courteous to show you have no hard feelings for the rejection. Others will tell you to move on.
The golden rule which seems to be repeated a lot is, if you don’t have something nice to say, don’t say anything.
Most of the time I decide to move on, especially if I get their default rejection letter they send out to everyone. Sometimes I thank them if the letter is personal.
However, on rare occasions I dare to challenge the rejection. Not in the sense of making them unreject me, but more in the direction of trying tell them, in a nice way, the way they worded the reason for the rejection was rather clumsy.
What I see as clumsy is if their reasoning to reject me is clearly based on presumptions, when it should be based on knowledge and experience.
Because when giving a reason to why someone was rejected, they should go, “ah yes, I see what you mean.” Not, “and you know this how?”
Which in itself makes you understand that the rejection wasn’t that bad after all.