Where can I find the explanation of usage of [Backspace] key?

The reason I am asking is because, previously, when I write an e-mail, it would automatically create capital "I" from the letter "i" I enter (obviously it is "thinking" that usage of i as I, like in word "me" is the most common). Also previously, in this case, when I would press [Backspace] button, it would change it to small letter "i". That was at least something.

Now, recently, without doing any changes, if I would do the same thing, the system would create small letter "i" in addition to capital letter "I". What's going on?

Thanks.