Setting LANG to tr_TR.UTF-8 did solve the issue.
Turns out LANG being empty was the root cause:
I only checked through ...
Thanks to your output of verbose inoremap <c-h> it's really easy to see what is happening here!
You are using the auto-pairs plug-in and it's installing buffer-local mappings for the bracket keys, but also for keys such as Enter and Backspace. It maps backspace so it can "undo" a close bracket action if you type backspace to erase a mistake of yours.