When pressing the backspace key, it puts  

[Ignatius Winarto]

It puts   in where you have used the backspace key when editing.

[Artur Formella]

Could you provide steps to reproduce this bug?

[Ignatius Winarto]

Actually, I just realised the backspace has got nothing to do with this. The   character appears when you press spacebar twice (or more), and so if you press spacebar twice then press backspace to correct it (i.e., you only meant it to be a single spacebar stroke), then you are left with   character in place of the first spacebar key stroke.

[Garry Yao]

I think it's not a bug, actually some browser collapse multiple, concurrent spaces into a single space, so always inserting spaces is not appropriate, so whenever you press 'space key', browser will:

1. Insert a normal space if there's no space around;
2. Otherwise insert  

This could guarantee that the visual spaces is always maintained and the line-break could be respected also.