Nope, sorry, but thanks for trying.
Not only for pointing out the undo feature, but also for using that
condescending tone, although if English isn't your native language I
will allow that you didn't mean for that, and all is forgiven 
Firstly, I knew about the undo feature, but it misses the point
completely. One wants to be able to turn off the autocorrect behaviour,
not just constantly keep undoing it while typing.
Secondly, it keeps redoing the autocorrection, such that one has to
constantly keep pressing ctrl-z, often almost immediately after just
having done so, and if one doesn't notice this, one has to potentially
undo a whole slew of typing, resulting in needless retyping.
Thirdly, it can get stuck in a repetitive cycle:
Open a blank Writer document and type "cat" followed by enter. See the
initial "c" get capitalized. Press ctrl-z to undo the enter, and again
to undo the capitalization. Hit end, and retype the enter. See the
initial "c" get capitalized. Wash, rinse, repeat.
Yes, you can break the cycle by typing a space after the "cat", then
pressing ctrl-z to undo the capitalization, then pressing enter, then
going back to the first line and deleting the space at the end of the
line and then going down to the new line. One could also open Notepad,
type the text in there, then copy and paste it into Writer. But that is
a bit tedious, and kind of misses the point of Writer, don't you think?
Paul