I updated my IDE, and this thing you can see in the screenshot(s) is now there - a vertical white line I cannot remove or change its color. So I went back to earlier commit, and that fixed it, but then I noticed there was a nice new function SetCaretPosInActiveEditor - I want that! So I updated to commit 1580d1778ea96d22b0fa9982f299e74402fa850e ("IDE: Improve setting cursor position in new programs. Issue #32089, patch by n7800."), but that white line is there!
Anyone knows how to fix it? I checked everything color-related in the Options, and nothing changes this white line.