Here's a screenshot. There IS actually a white border around the text, but it's very very thin. Notice the "101" text in the lower right corner? Even at this larger-than-tablet magnification, it's very hard to tell there's any separator.
BTW, I held the tablet - from which I took the screenshot - up against the LCD monitor on which I'm viewing this post, and the attachment preview shown below is only barely smaller than the matching image on my tablet. So that preview is a pretty good approximation of reality, though of course at lower resolution. This is why I need 150% or more.
Also, Locus beta 3.40.2.1 here is going nuts, drawing and redrawing the labels at two wildly different sizes. Here I've caught a screenshot with both sizes shown at once. Panning seems to trigger some re-rendering, and I had to pan a lot to line up things for the screenshot.
This is using a recent OAM V4 map with your latest (I think) Elevate theme. Thanks for looking into this.,
I have to disappear shortly from the internet for a few days, sorry.