This is an enhancement request for a visual indication after using command 'Edit > Track Changes > Compare Document...' and when there is no difference in both documents.
Now LibreOffice does nothing and it's not seeable for the user, if the comparation was done successfully or there was a problem so that it hasn't started.
This visual indication could be an empty track changes dialog with a note that all is identical or it could be an infobar.
I confirm the current behaviour with
Version: 126.96.36.199 (x64)
Build ID: dcf040e67528d9187c66b2379df5ea4407429775
CPU threads: 4; OS: Windows 10.0 Build 19042; UI render: Skia/Raster; VCL: win
Locale: de-DE (de_DE); UI: en-GB
cc: Design-Team for further input and decision.
In general I would support this idea, but a look at meta bug 125647 shows, that LO actually can't compare everything. So an information "There is no difference" could be critical.
We discussed this topic in the design meeting.
It's a rare use case and not worth much effort. So simple solution would be the best, which is a confirmation box.