Because this visual artifact shows up on your physical device but not in Chrome for Desktop's Device Mode emulation, I wonder if this may be some kind of CSS or other rendering issue rather than a character symbol in the DOM. In my experience, device mode is faithful to how the site should actually look on a physical device.
I would try clearing site data on both the physical device and Chrome for Desktop to rule out any difference in state. Then if the issue still occurs on the physical Pixel but not on the emulated device, you could try attaching the Chrome debugger to your phone using Chrome's Remote debug Android devices feature. Using the debugger, you could use the Elements view to scan the DOM for anything that could be causing this on the physical device, then compare to the Elements view on the emulated device.