It's likely a joke, but it sure stands out. Could also be transcription error. The letter itself contains a typo ("if you will privide") which is fixed in the transcription. (It should have been transcribed as is with "[sic]" added to note the original typo.) Too bad there's not an image of the reply.
BTW, the letter was shared to reddit 7 years ago and a redditor replied that it was his uncle Andy:
What kind of amazing self-parody is 'Irmo man wrote letter'! That's brilliant