Currently, on my system, comments default to being directed left-to-right. To change this, I'm not supposed to edit a full-blown style; instead, I choose "format all comments" in the drop-down menu each comment has. Well, the thing is, the "format all comments" dialog doesn't include the comment paragraph direction (LTR/RTL). Which it probably should.
I confirm it with Version: 6.0.0.1 (x64) Build-ID: d2bec56d7865f05a1003dc88449f2b0fdd85309a CPU-Threads: 4; BS: Windows 10.0; UI-Render: GL; Gebietsschema: de-DE (de_DE); Calc: CL
We now have a Comment paragraph style. So we can set the direction of all comments - though not with "Format all comments..."