As you already know, automatic removal of blue words can be turned off in the Settings for the Reader.

However, this just means that when you click the complete Lesson option on the last page, all your blue words for the whole lesson will be moved to known. There is no reason to keep blue words. The idea is that you either need to learn them or they are known. (or you can ignore words).

Having said that, you can click on all white words to make them blue again and create LingQs for them. So, if you are reading, and come across a word you incorrectly marked as known or ignored, just click on it to make it blue.

Finally, you can reset your language in your Language Settings - https://www.lingq.com/settings/languages

Hope this helps! Let me know if you have any other questions.