Have never encountered a situation like this, but the tip someone gave about (carefully) removing staples yourself (e.g., from the departure card) before going through immigration rather than risking an IO tearing out the stapled departure card and possibly leaving a rip on the visa page sounds like good advice.

The thing about applying tape to the "back" of a torn visa page is that the "back" of one page is the "front" of another, and I can sort of see that catching an IO's attention as he goes to apply a stamp over tape... 'Way up in the corner as in the OP's case doesn't seem like it should be a big problem though. I would just make the repair job as inconspicuous as possible.

When I was a bookseller I used a tape called 'filmoplast', made by Neschen in Germany. It was perfect for almost invisible repairs of white paper. It is expensive and a bit fiddly to use. Someone may sell short strips of it on Ebay, as I used to do.

Germany makes those poor passports...in 4 years I needed 2 because the first page fell off... Plus once it drops into water, the front and back of it macerates as it is made out of unlaminated cartoon (picture an antique book made in a bookbindery and take it accidentally for a swim...). I think the only passport in the world which does not have a laminated front/back.

I have so many old staples in my passport, along with ones for my current TM6, my 90 day report, and the receipt from my TM30, that it sets off the metal detector....