General friendly discussion follows:
Darn, I am trying to kill AbstractDataStore classes. Would of loved to know what permissions were getting in your way. The geotools-devel list here is for exactly these kind of questions.  
It was over a year ago...  IIRC, it was the final modifier on ContentFeatureStore.addFeatures.  I actually remember visiting the GitHub page and seeing that the top commit fixed my problem on master.  Sadly, I had to make it go with a release version that day/week:(

Understood. 

I'll see if we can spend a few minutes and switch over to Content** implementations, but it might take a little while.

That would be excellent, I would appreciate any/all questions/feedback as I am setting up for a foss4g workshop on using ContentDataStore. It is already much easier to teach then AbstractDataStore with a more consistent design and well defined objects (rather than magic HashMaps).

Anyhow, is a back-port to the 11.x series possible?  In reality, that likely only matters if the 11.3 release will come before the 12.0 release...

Awesome; I think I had run across another schedule/release info which didn't have 12.x on it. 

Backport is 11.x is possible for any bug fix, and even new features (as long as they do not change the API). So this qualifies. We are not too strict, but do try and keep communication going.

You are also welcome to attend the bi-weekly Skype chats - this is especially recommended when you project gets near release and would like to carefully co-ordinate patches/fixes.
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Jody