"Must use punctuation at the end of a sentence in order to keep the d large case."
That is DEFINITELY a system setting on your computer...
Are you by chance using a smart phone or a tablet?
That would explain a lot if you are. The "I'm going to be helpful and change your entry to what I think it should be" setting is a bit of a pain at times.
"The gift which I am sending you is called a dog, and is in fact the most precious and valuable possession of mankind" -Theodorus Gaza
Baby Jesus cries when the fat redneck doesn't have military-grade firepower.