It's still a lowercase i!
What you are experiencing seems to be a combination of a custom font on the website and a small font size. It is simply not large enough for your screen.
As you say, zooming into the text on the page makes the white space between the dot and the rest of the i visible. This proves that the problem is the resolution of your screen, which does not provide a pixel size small enough to display the white pixel below the dot.
There are two workarounds (not solutions) I can think of:
Slightly increasing the zoom level by about 10% is an easy workaround. It's quickly done and browsers keep the setting for all tabs (at least Chrome does).
If you really need a permanent solution, a user script plugin like Greasemonkey (Firefox) or Tampermonkey (Chrome) might be a way to automatically increase font sizes on small text elements. You will have to know some JavaScript, as a complete tutorial would be out of scope of this post.
Ctrl
++
)? Does the dot separate from the i or do they still stick together?