DEV REPLY BELOW:
"Why do you think this addon should prevent loading pinned tabs on start? :)"
In other words, it doesn't prevent activation of pinned tabs.
I think it should be called "add a pinned tab at the right" or "Dont switch to pinned tab when tab closed" or something arcane like that.
I don't need a addon to create a blank pinned tab.

Works well in default configuration ("new tab page" is blank page), but stops working completely when switching "new tab page" to home page (the one I actually wanted when installing it)

It does exactly what it says in the description. And it works great for common use cases. However, it doesn't suit me. I currently have 473 tabs in the current window (most of them are discarded and hidden). To manage so many tabs, I use this group tabs extension (https://addons.mozilla.org/en-US/firefox/addon/power-tabs/). So, when using these two addons together, it is expected that a new tab should be opened every time there are no VISIBLE (not hidden) NOT PINNED tabs on the tabbar. For now the focus just goes to the rightmost pinned tab. Adding this feature would be quite justified, as the user community of certain group-tabs extensions is quite large

this one worked a bit nicer than the others, handled it better if i did something stupid like just hold down ctrl+w like a drunk moron. also the bit where it opens a new tab if you just pinned the last tab you had is dope.

Great add-on. Works as advertised, I have relied on it for some time. At least it DID work until just recently. I am using Firefox Nightly, and this extension has quit working as it has in the past.

Update: This was some sort of incompatibility with Firefox Nightly. After todays update of Nightly, the extension works as it always has. I have 4 tabs that I keep pinned at all times. If I close the last Tab in firefox this extension creates a new blank tab rather than making one of my pinned tabs. Great add-on. Many thanks to the developer.

Doesn't work. Pined tabs are still loading on start.

Because that is what was written in the title: Do Not Auto Activate Pinned Tabs :)

Если открыть пустую вкладку и нажать на неё пинед(pined), то браузер не будет закрываться.
if you open an empty tab and click on it (pinned), the browser will not close.