When are they going to support Opera (browser) in Browser Cleanup?
Welcome to the forum. 
Probably when it becomes more popular. Safari is probably not covered for the same reason.
Here are some statistics:
http://www.w3schools.com/browsers/browsers_stats.asp
I would say it is time many more people should be going to use Opera.
A really good browser and faster than others.
I like Opera however its lack of support of extensions in general is why I dont use it. That is the main reason I use Comodo Dragon. Ive tried Firefox but Ive always had problems with it being slow, crashy, and memory hog.
Opera 15 and above with Blink rendering engine has many extensions to choose from.
https://addons.opera.com/en/extensions/
It also supports many Chrome extensions from Chrome Web Store if you install Download Chrome Extension.
https://addons.opera.com/en/extensions/details/download-chrome-extension-9/?display=en
Like you,I am also using Poper Blocker in Opera Developer.
I did some searching online and failed to find very many good reviews about Opera v18
It’s a chromium based browser and seems to lack many features most users rely on.
I tried Opera once and quickly figured out it’s more of a PITA than it’s worth.
So the question is, why use something when more robust browsers are available?