I'm back. Here's the story: this bug totally happens, but it's not quite straightforward to reproduce, I admit. I almost convinced myself I cried "wolf" for nothing. Attached is a capture and a text file with text to reproduce the bug systematically.
Paste it in a new configuration module, or text template, doesn't have to be code, or just open it with File->Open in Designer mode. "Works" in any recent training or enterprise version. Search for the full word "a" (simple search or global search) and be amazed.
It will find the single "a"s in "a hare a fox" but also the final "a" in "aaa baa kaaa". Yes, they're identical "a"s, written all at once with same keyboard layout, no practical joke here (tee-hee, I took the bait once with a "CurrentRow" variable name written with an initial russian "es" which is indistinguishable from a latin C, but whole different Unicode).
And no, even if the results are above the double line, I cannot erase the code below, or some search results from above will disappear (?!?), even if I erase a comment line. Strange or what?