What Zanna said is 100% correct and self answers are encouraged but the down votes have nothing to do with self answers, as the questions were voted up.
Let's look at your answers
Dell Inspiron does not go into GRUB after shutdown from Kubuntu
I think I found the answer. I disabled to Legacy ROM option in the
BIOS settings while leaving UEFI enabled. After reinstallation the
laptop now boots as expected.
I didn't try disabling UEFI completely since I prefer that mode.
Saying you think you found the answer, is not what the answer box is for, it seems like a guess rather than fact, this will always attract downvotes here, be sure of your answer.
Dropbox ZIP appears in Downloads folder
Found it. KTorrent was downloading some crap. No idea where it came
from since I have never used torrent before. Anyway I removed KTorrent
Swearing is never good and how did you remove Ktorrent? It could be explained better.
Avoid flooding disk by copying to failed mount point
I could solve this by removing writing rights from the dummy mount
point folder. This way, copying files fails if mounting was not
This one lacks details, you talk about beginners understanding in the comments above, how would they understand "removing writing rights from the dummy mount point folder"? Answers should help anyone who reads them.
I personal may only downvote the Ktorrent one, it is not helpful because it has no detail or context but I could see why all three would attract downvotes.
The basic thing lacking in all these answers is detail, how did you do this? Just saying "I did this" does not help people, it just confuses them move.
You put far move effort in to the questions, that is why they have upvotes and the answers have downvotes.
I hope you take this the right way and edit and improve your answers to make them high quality, then you will get upvotes.