There’s a really bad behaviour of Firefox when pasting a text containing non‐breaking spaces ( ): these special characters are converted
into normal spaces. That’s completely useless considering that the thin
spaces ( ) are not converted!

The problem has been reported upstream as bug #359303 thirteen years
ago, and it’s still not fixed! Actually, it is considered to be a “feature”! I think that nowadays it’s rather a very annoying bug. I can enter this special space with my keyboard in a text field, but I can’t paste a text containing it in the same field ; and if I paste something containing a thin space, it works. What a strange design!

All Firefox versions are concerned.

Steps to Reproduce:

1. copy a document containing non-breaking [ ] and thin spaces [ ], for example from Gedit editor with the “Draw spaces” plugin activated (Gedit → Preferences → Plugins → Draw spaces, then click on Preferences button and check “Draw non-breaking spaces”), so you can see them;
2. select the text with the special characters, copy it and paste it in a Firefox form input (text or textarea);
3. now copy the pasted text form the Firefox input back to Gedit, you’ll see that non-breaking spaces have been replaced by normal spaces whereas thin spaces are still there.

The trivial patch here attached has been proposed. It would be nice to see this insane behaviour nuked a least from Mageia!