Hide Element Button greyed out or disapear on certain sites

[HLC1890AT]

With all versions of Adblock Plus (Firefox, Chrome, Opera ...), the button "block element" is grayed out or this button disappears squarely when I'm on facebook, youtube, but not on other websites . Why certain sites allows Adblock Plus to prevent users from hiding elements?

[mapx]

known bug FF / ABP, still unfixed

[HLC1890AT]

Thanks you for answer, I precise, this bug concern all versions of ABP 3.0 (not only on firefox). I precise also Ublock Origin don't have this problem. Weird.

[mapx]

https://issues.adblockplus.org/ticket/5938
https://issues.adblockplus.org/ticket/6714

[HLC1890AT]

Thanks you very much, good luck for trying to fixing work.