My life was significantly improved when I discovered control shift paste, which pastes just text without format. But un-desired formatting of text remain the bane of my life.
Off-topic, but a somewhat similar experience for me was learning about Alt+select. Allows you to select parts of a hyperlink without actually activating the link. (At least in Firefox.)
When you first hear about it, you think "What's the big deal?", but then you quickly find that you use it pretty often.
So essential - how often would I want the formatting in the obviously completely different context? I used to paste things into the URL bar to remove formatting. I've discovered a colleague does the same.
You might want to be careful about pasting anything remotely sensitive into the URL bar as most browser automatically send your query to the search engine for auto-complete functionality.
I never changed my habits from Windows; I use the Run box, or type leafpad / mousepad. It's interesting that we've independently invented the same technique.
GitHub started mangling text some months ago and it bugs the hell out of me. It's also completely unnecessary as GitHub already links things like @user, #123, and deadbeef (for commit hashes). I just want to copy the exact literal text I see; why does that need to be hard?
You can set "dom.event.clipboardevents.enabled" in Firefox to disable all of that, but some websites can break horribly because they just assume it's there and will do $weird_shit if it's not. e.g. Twitter and Facebook messenger for example; it's not that you get an error either, it just behaved in really odd ways. It seems Twitter works now in quick test, and I no longer need to use Facebook Messenger, so let's try setting it again.
There's also "clipboard.plainTextOnly", but it doesn't seem to work, or maybe it does something different from what I expect.
When you first hear about it, you think "What's the big deal?", but then you quickly find that you use it pretty often.