Good point—because composition doesn’t tend to look like regular, selection-replacing input, it wasn’t going through the replaceSelection path. The patch below should help with this.
Thank you for your support during your busy schedule.
After that, I noticed that there was a problem with “placeholder” that seemed to be related.
If you enter CJK while “placeholder” is displayed, the first composition will be forcibly terminated.
I expect this bug to be fixed in the patch as well.