No, no, I didn't ignore your suggestion, I tested it right away but it didn't work in my vba code.
Now I've just tried it again, I didn't set the revision tracking again, but it gives nothing, no replacement is made.

I've just run several tests in Word with Ctrl+H and this is what I get:
- if I remove the track changes and the cursor isn't between the ... and the H (Hi...|Hello!) the capture and replacement works fine. If it's between the ... and the H, nothing is found and replaced.
- if I leave the modification tracker on, the replacement is nonsense (HiHello...!).

So we can probably deduce that track changes have something to do with it, but I don't know how to do anything more in my code than use :