I read now a 1100 pages (on stock reader 850) book, and it is very slow on stock reader, and it seems annotating (why I used the kobo reader) makes the database unusable. So I am happy with koreader speed and not spoiling the database

. (Though I will check it, as I used both stock reader and koreader when the database killed itself, but it is my understanding, that koreader does not change the files).
Does it cause problems to use kobo original reader and koreader on the same file usually?