This seems a bit bonkers, and I know it will annoy people. If they are ignoring some muppet, they want to see as little of said muppet as possible. People do not want to see all of said muppet's details every time they scroll past a post they want to ignore. This was one of the things most requested when implementing ignore via a mod way back in 1.1.x.
So, this seems to be the sensible thing to do:
// Show information about the poster of this message.
echo '
<div class="poster">';
// Show information about the poster of this message.
echo '
<div class="poster" ', $ignoring ? ' style="display:none;"' : '', '>';
A similar argument applies to various other elements in posts. Particularly on mobile, when there is more than enough crud to scroll past anyway. Are people who want to ignore a post really going to want (for example) custom fields below a post still displaying?
It would make more sense to strip down the visible content of ignored posts to the absolute minmium necessary for the page to function. :)
Related to this: if unwanted content by muppets you are trying to ignore is going to be hidden, IMO this also makes sense...
Ignored users: hiding posts on Recent.template.php (https://www.simplemachines.org/community/index.php?topic=569669.0)
It's extremely easy to implement. Just requires an extra global, a basic if (()) else (()), and a suitable bit of text for "You are ignoring this muppet" (which could be nicked from Display.template.php).