What the person using those links does not realize is that a Creative Commons license relaxes restrictions rather than imposing additional ones.
Everything you create is already protected by copyright by default. If you publish an essay and don’t append any license to it, nobody may republish or remix that essay without your permission, unless an exception like fair use applies. The exact restrictions will depend on local laws.
By using a Creative Commons license, you choose to forgo some of those copyright protections. Thus the comments of the person you replied to are actually less protected than yours or mine.
Your instance will still exist, and federation should continue as normal if you manage to reclaim the original domain.
If you have to switch to a new one, however, federation will be very awkward. Other instances will essentially treat you as a brand-new instance, and mirrors of old content will be “orphaned” and no longer sync.
Vivaldi also has a “window panel” that is basically a tree-style list in your sidebar of all your tabs across all windows and workspaces, and recently closed tabs and sessions.
Vivaldi’s toolbar can be customized just like Firefox, but you additionally also get a bottom bar and a sidebar to place toolbar buttons on.
Vivaldi has a Spotlight-like search bar you can open with F2 to quickly find a page in your history or type any browser command like hiding the UI. You can also string multiple commands together and add them as a toolbar button.
You can add websites to your sidebar too to open them in a slide-out window of sorts (basically the same thing as Opera GX’s sidebar).
You can tile multiple tabs to open them in a split or grid view, which I haven’t found a way to replicate on Firefox so far.
And as someone else already mentioned, I personally find installing CSS and JS mods to be a lot more accessible on Vivaldi.