The example post I have has since been deleted but here is the link for folks that can see it: https://ell.stackexchange.com/questions/177285/is-this-sentence-the-one-people-usually-use
When I viewed that post on my phone I thought it was odd that user didn't have a new contributor indicator and found that they did have the indicator when viewed in the full site. I noticed this before the question was deleted or put on hold.
The screenshots below are taken in the same browser (Firefox, which I'm also using on my phone) on my iMac (so it's not a screen size issue). I have ad-blocking disabled for Stack Exchange sites. At the time I noticed the question, I asked in the Teacher's Lounge (message 46393692) and other people saw the same behavior, so I don't think the issue is due to my environment.
And looking at those screenshots, I just realized that I have a popular (for moderators) Tampermonkey script active. Here is a screenshot with Tampermonkey disabled:
I don't think it is an issue with the moderator scripts, because the folks in the Teacher's Lounge that confirmed the issue weren't moderators on ELL.