Expandable bundles (T114356), provide a compact version of the notification messages (T127813).
Some of those messages (Flow-post-reply, and Flowusertalk-post-reply) include an excerpt in their bundled version.
The excepts on those bundled notifications should be shown in grey (in the same way excerpts are shown in non-bundled notifications). According to the screenshot below, the above seems not to be the case. So adjusting the style may be needed.