OK, I found the trick (just a dirty workaround) :
in flarum\vendor\flarum\core\js\forum\dist\app.js
on line 26700, I added :
.replace(/\n"/g, '\n "')
In context :
key: 'data',
value: function data() {
return {
content: this.content().replace('/\n"/g, '\n "'),
relationships: { discussion: this.props.discussion }
};
it adds a space before the " when it is placed in the beginning of a line.
The source of this code is in :
flarum\vendor\flarum\core\js\forum\src\components\ReplyComposer.js
