If you get a notification involving a revision which was suppressed before you saw it, you get this message:
Example mentioned you on the Example talk page in "This page revision has been suppressed.".
Links in the above are
<Example> → User:Example
<Example talk page> → Talk:Example
<This page revision has been suppressed.> → Talk:Example#This_page_revision_has_been_suppressed.
The suppression message is getting treated as a section ID, trailing full stop and all, which is obviously incorrect.
There doesn't seem to be much point in delivering such a notification, but by the looks of it that would be complicated. Echo appears to be pulling the page title at the time the user asks to see the notification, by which point it's gone. Perhaps Special:RevisionDelete could pass suppressed revision IDs to Echo at the time of action, saying "cancel any unsent notifications relating to this revision"? Seems like it might take some work to do though.
Failing that, I'd suggest a correction of:
Example mentioned you on the Example talk page, but that revision has been suppressed.