Hi,
When you click on the “reply” option in a Comment or an Answer, a box opens with the ID of the user that you wish to reply to.
The error is that inadvertently the reply may be sent to the wrong user if you don’t notice that only a part of the user ID is highlighted in blue - not all of it, presumably because that part of the user ID is already in use. If the user ID is not already in use then the problem does not occur. The user ID (or part of it) is not highlighted in blue
Here are some images that show what I mean
In the first image below, in the left image I replied and the box opened as shown (see green arrow pointing towards the user ID). However when the reply is submitted you will see that the user ID is different when you look at the right side image, part of it is highlighted in blue (red cross)
The second image shows where the reply would go (see red box on left side)
If you are aware of this you can prevent this from happening if you place a space between the @ and the user name then it should end up at the correct user or at least not be sent to the wrong one (see 1st image green box on left side and 2nd image green box right side)
Here are some images that show the problem.
Hopefully this makes some sense to you.