I am not ready do decide whether I want to use my full Google+ name on YouTube. I would like to keep using my YouTube nickname for now but be able to switch to the full name later. But YouTube keeps asking this question frequently and does it with a blocking pop-up dialog. Is there a hack to get rid of this? Maybe some cookie to set, some userscript or something particular to filter-out with AdBlock+? Or, maybe, the choice is going to remain available somewhere in settings if I choose "no"?
You can tell it no for now and it will stop asking you. Then, if you decide you do want it to use your real name, you can update this in the YouTube settings. To make this change in the future, login to YouTube and click on the dropdown menu next to your name/picture (in the upper right corner) and select Settings. From the overview settings screen, you should have an option that says Link channel with Google+. Clicking this will bring back the "use your real name" options that you are trying to avoid at the moment.
In AdBlock Plus or a similar browser extension that can use ABP filters, simply add the ff. as a custom filter:
This will make Youtube stop asking for your real name.
Source: Comment by user dmurrow_ at Reddit /r/self post, "For f--k's sake Google, I do NOT want to use my real name on Youtube, you do NOT have to ask me again later, since I will answer NO, just like the last fifty times"