I do see some issues with the code
1. misplaced url property
<div itemprop='itemListElement' itemscope itemtype='http://schema.org/ListItem'>
<meta itemprop='url' content='/u/elvis'>
<a href='/u/elvis' itemprop='item'>
<span itemprop='image'>
<img width="45" height="45" class="avatar" src="https://sea1.discourse-cdn.com/flex001/user_avatar/forum.reflex.dev/elvis/45/31_2.png">
</span>
<span itemprop='name'>
elvis
- elvis
</span>
</a>
</div>
The itemListElement is a ListItem.
The ListItem has a property item which is a Thing.
A ListItem can not have a url property
A Thing can. See ListItem - Schema.org Type
Hence, the <meta itemprop='url' content='/u/elvis'> line should be moved two lines lower within the item property value.
<div itemprop='itemListElement' itemscope itemtype='http://schema.org/ListItem'>
<a href='/u/elvis' itemprop='item'>
<meta itemprop='url' content='/u/elvis'>
<span itemprop='image'>
<img width="45" height="45" class="avatar" src="https://sea1.discourse-cdn.com/flex001/user_avatar/forum.reflex.dev/elvis/45/31_2.png">
</span>
<span itemprop='name'>
elvis
- elvis
</span>
</a>
</div>
2. missing position
This one is a bit more subjective. Google says here Carousel (ItemList) Structured Data | Google Search Central | Documentation | Google for Developers that the property is required
So Google says “it’s required”.
That means “Google requires it”, not “it’s required by the schema”.
3. broken Schema.org validator
I don’t know what it’s doing but it’s not correctly validating. It should have caught #1.
