Why did the "system" display two different usernames for the same question, depending on the way you accessed the question?

Question

I do not understand how the site displays usernames. And in the case of the question What is the difference between “get mad” and “ get angry” in this paragraph?, I found this has been very interesting. Perhaps someone who can look behind the scenes, perhaps by tracing ISPs, can be of some help.

The current username attached to this question is tiengvongdemkhuya. This is an unregistered name. I am not sure if the same unregistered name was listed yesterday, but that is not important to me.

Now comes the confusing part. I know for sure yesterday (as in 100% for certain) while I was accessing the site by mobile phone, probably on mobile view, that the following was the case:

When you were looking at the active questions queue, the question was listed as having another user. I will not state the name of the user that this view gave for it, but it was a registered user with not a small number of rep points. I say this only to show that it was not someone close to being a beginner here. The point is, is that this view did not show the unregistered name but a registered name.

This question is about the system of how the site displays names. Because yesterday there was certainly a discrepancy between the username listed at the actual question page, and the one listed at the active questions view. Why did such a discrepancy exist?

Answer 1

Here's what happened. We have a user that was creating a new account each time they had a language question about a particular source text that is offensive to some. One of the several questions this user asked was fairly controversial and sparked some discussion, and there was disagreement about whether the question was off-topic.(https://ell.stackexchange.com/q/105681/9161).

A completely different user posted an answer to that question and later decided to delete it, and ask a similar question (What is the common meaning and usage of "get mad"?). I actually think this was a proper response to the controversial question. It's OK to post a new question that was sparked by something else on the site as long as it isn't a duplicate, and taking the controversial source material out of the equation helps keep everyone focused.

Because this user was the last person to modify the controversial question, there was some confusion about whether they were the author of it because of the way the user names of the last person to modify the question are displayed in the mobile version of the site. The authors of these two questions are not the same person, as far as I can tell.

If you see something that seems suspicious, please flag it for the mods instead of confronting the user directly in comments. We do have access to non-public information that can help resolve questions about authorship and such. We are not able to share that information with the community, so it's better to just let us investigate and take appropriate action.

Answer 2

I'm going to post an answer. There is no bug in the system. The "mystery" has been resolved thanks to @kiamlaluno's help.

What Alan Carmack saw on his mobile screen was the name of the user who answered that question, but later chose to delete their answer.

Every time a user answers a question, the post appears on the "active page" and visitors will see that person's name appear on the screen. Unfortunately, for Alan Carmack, he doesn't have enough rep to see deleted answers and so he made the assumption that the answerer and the OP were one and the same.

Please note that the user @tiengvongdemkhuya is an unregistered user, and the question has not been edited.

This is a screen capture I took a few minutes ago from my laptop, users who modify or answer questions will have their avatars displayed next to the question.

I would take a screenshot of the deleted answer, but I do not have 10k rep, but I trust kiamlaluno comment to be 100% correct (obviously, the post deleted was an answer, not the question.)