Personal Settings > Use WYSIWYG editor - it doesn't get stored. If I save it to Yes and then I get back to Personal Settings, it's still No. It's not stored in serendipity_config table (where it used to be stored in v. 1.7).
Also, 1.7 used to have a site-wide WYSIWYG config option, that was stored with authorid=0. Now I don't see it anywhere in site configuration.
That is when running commit e12b998bf7 from github, installed with SQLite.