Hello. The following problem might only concern the French Wikipedia (but I doubt it).
For a notification to work, it must be associated with signing in the same editing process.
This fact is generally well known to the most experienced users. However, this procedure is not enough to make a notification valid, as evidenced by the following links:

• https://fr.wikipedia.org/w/index.php?diff=156306853
• https://fr.wikipedia.org/w/index.php?title=Discussion_Wikip%C3%A9dia:Conventions_typographiques&diff=156339923&oldid=156339722

In these two examples, I did not receive any notification. As you can see, my correspondents nevertheless notified me and signed in the same instance.
I am inclined to believe that a new line (carriage return, line break) must also be included in the same instance, but that is only a vague assumption.
Be that as it may, this strange behavior of the software causes even the most experienced Wikipedians to err without knowing it. So I would appreciate you correcting this problem (and if after you could tell me where the bug came from, it would be great).