How can I repair my old and expired passport?

I hold an Indian passport. My old passport that is now expired has suffered a lot of wear and tear. Any time an immigration officer, travel agent, or passport officer takes a look at the expired passport, they remark that the expired passport is damaged. They do mention the word "damaged" in their remark.

Nature of damage: The cover page of the old and expired passport has for the most part separated from the threads that bind the cover page to the rest of the pages. I am scared that very soon the cover page would begin to dangle from the rest of the passport or even completely separate from the rest of the passport. Here is a picture that shows how badly the threads have cut through the cover page binding area which has caused the cover page to begin to separate from the rest of the passport.

My new and current passport is fine. When I realized that the old passport is damaged, at first I asked an officer if I could simply use glue to repair the damage. I was strictly advised to not apply glue and instead apply for a new passport. Several discussions on the Internet also advised against applying glue. So I did apply for a new passport and the new passport is in good shape.

Often while applying for visas for certain countries, I need to submit my expired passports too because the consulate wants to see my travel history, so I am curious to know what to do with the old passport.

Question: Now that I have a new passport, can I repair the damage in the old passport with glue? On one hand, I am worried that the cover page may completely separate and fall off from the passport with more wear and tear, so it should be repaired somehow. On the other hand, I am also worried that if I try to repair it, it may be seen as tampering with the expired passport by a consulate when I submit my expired passports during a visa application. What's the right thing to do here? Have you had such an experience?