Sadly, it’s always been this way.
I always hated trying to help someone, going to the Game Guide to double-check the Properties on a Legendary Gem and realizing I either had to go to a third-party website or run the game to get this information. 
Testing
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Test 123
https://imgur.com/gallery/OFNqu8z
This is a test. I’m replying to my own post.
I’ve seen a post said “@name” will notify the person, but I can’t find that post.
@Perusoe
Do you get a notification?
@Boubou
Do you get a notification?
Nope.
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Yes. But, only because I created this thread.
⤺ 4 replies Perusoe’s Testing Grounds
ic
(twenty characters)
@Maskraider-3992
@Maskraider#3992
Hi.
Nope. No notification 
The Gaming Community that I am a member of has this feature too. What I like about it is:
- When used, it puts the callout in a highlighted box, which looks like this, @username.
- It sends a notification to that user the next time they sign in, complete with an audio sound, and also through an email they used to register with, depending on their Profile Settings.
- If you click on it, you are directed to that user’s Profile.
I wish these new D3 Forums worked that way too. 
I believe @MissCheetah first posted this. But, I can’t find it now either. Let’s see if she gets a notification and responds here. (It may only work when calling out to MVPs or Moderators, etc. Or if they call out to us).
I seriously doubt the Blues/MVPs want to be notified evertime someone flags them within THIS forum.
@Perusoe @Boubou @DogBone
I’m reading Discourse New User Guide.
@name supposes to notify the person. Don’t know why it doesn’t work.
See Mentioning and Notification sections.
Mentioning
To notify someone about your reply, mention their name. Type
@to begin selecting a username. This search will also search the name fields in case you don’t know a particular username.
Notifications
When someone is talking directly to you — by replying to you, quoting your post, mentioning your
@username, or even linking to your post, a blue number will immediately appear over your profile picture at the top right.
This is actually how it works in the Gaming Community forums I mentioned above. First, you type @. Then, as soon as you type the first letter of a username a drop-down menu appears that lists all the users whose username starts with that letter. As you type more letters, the list is filtered to usernames that start with that combination of letters and so on.
This is what it looks like after typing just a few letters:
If I continue typing letters I can eventually select my username. Notice that as I mouse-over the “mention”:
- The cursor changes.
- The “mention” is clickable.
- A brief Account description pops up.
- Punctuation can be used without deactivating the “mention”.
Like this:
And, if I click on it I will be taken to my Profile.
Yes. These new D3 Forums are currently working this way.
I don’t know why the “mentions” aren’t working. Either Blizzard’s web team still has some tweaking to do or maybe they decided to disable this function. 
Found it!
Or at least one reference to it. 
That need the person to select the option first. How could I know if he has done that?
The default preference is auto-tracking the thread if I had posted before or entered a thread 4 min before. (See Preferences for details.)
So, unless @Boubou had changed the option before, otherwise he should have received a notification from my previous test. But he didn’t.
Ok, this thread is “Tracking” status to me (was set by auto-tracking).
If you reply to your own post and mention @Maskraider, I’ll receive a notification, I suppose. Try it.
@Maskraider
Did you get a notification?
Note:
- “Watching” always notifies you.
- “Tracking” is supposed to notify you “if someone mentions your @name”.
- “Normal” is supposed to notify you “if someone mentions your @name”.
- “Muted” never notifies you.
No. I’m not notified.
@username not working.
Okay. Thanks for confirming. 
Testing with @Maskraider-3992
Does that work to notify you?