bug#28339: 25.2; Emacs shows ZWNJ character (Zero Width non-Joiner) as Space

[handa]

In article <83wp52od4m.fsf@gnu.org>, Eli Zaretskii <eliz@gnu.org> writes:

> I thought that the shaping engine returns to us a series of grapheme
> clusters that completely replaces ZWNJ and the neighboring characters,
> and that therefore we only need to display the glyphs returned by the
> shaper.  If one of the glyphs returned by the shaper is ZWNJ, then
> isn't the shaper doing a poor job?

Each Arabic character constitutes a grapheme cluster.  Then, for the
sequence "0646 0645 06CC 200C 0634 0648 062F", to which neighboring should
200C belongs to?  Does Unicode define it?

Anyway, is it convenient or inconvenient to be able to edit ZWNJ directly?