I see this on Linux, too. I think it's something to do with how we're interpreting the answer responses.

It's probably this code:
    // Verbatim results don't get suggestions and hence, answers.
    // Scan previous matches if the last answer-bearing suggestion matches
    // verbatim, and if so, copy over answer contents.
    ...
https://cs.chromium.org/chromium/src/components/omnibox/browser/search_provider.cc?l=975-992

which means for verbatim suggestions with answers, you're displaying the answer as it appeared the last time it was received.  Its bolding should be recalculated.

 Issue 820697  has been merged into this issue.

 Issue 829810  has been merged into this issue.

 Issue 834798  has been merged into this issue.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/65c51f302123e4c46042fb2c2e0a244a28b87bcc

commit 65c51f302123e4c46042fb2c2e0a244a28b87bcc
Author: Justin Donnelly <jdonnelly@chromium.org>
Date: Thu Jun 14 13:35:38 2018

[omnibox] Fix for last character of an answer could be incorrectly bold.

The first line of answers contains text and bolding that's calculated
server-side. That calculation is nearly identical to what we do Chrome-
side for non-answers. This change makes it so that we use the Chrome
calculation to avoid the problem were an old-but-still-matching answer
could be copied to the what-you-typed match and have the wrong bolding.

Because the first line of answers can have some additional text besides
the query, that additional text is added in a separate step.

Because we're no longer using the server-provided bolding, which used
HTML <b> tags, we no longer need the parsing of those tags that we were
previously using.

Finally, since there was code moving around in omnibox_text_view.cc
anyway, I made some simplifications based on the fact that this class
only ever has one render text.

Bug:  721820 
Change-Id: I816c55cf9ff680dd922a18ef4cb9301543e1de25
Reviewed-on: https://chromium-review.googlesource.com/1070506
Reviewed-by: Dave Schuyler <dschuyler@chromium.org>
Commit-Queue: Justin Donnelly <jdonnelly@chromium.org>
Cr-Commit-Position: refs/heads/master@{#567248}
[modify] https://crrev.com/65c51f302123e4c46042fb2c2e0a244a28b87bcc/chrome/browser/ui/views/omnibox/omnibox_result_view.cc
[modify] https://crrev.com/65c51f302123e4c46042fb2c2e0a244a28b87bcc/chrome/browser/ui/views/omnibox/omnibox_text_view.cc
[modify] https://crrev.com/65c51f302123e4c46042fb2c2e0a244a28b87bcc/chrome/browser/ui/views/omnibox/omnibox_text_view.h