liveblog_features filter appears not to run

I've been trying to disable the hashtags feature using variations of this code:

```
add_filter( 'liveblog_features', 'mytest_liveblog_features', 1000, 1 );
function mytest_liveblog_features( $features ) {
$features = array( 'commands', 'emojis', 'authors' );
error_log( 'features is ' . print_r( $features, true ) );
return $features;
}
```

I tried unsetting hashtags if it was the value in a `foreach`, which also failed. I've also tried using various priority numbers (-1, 0, 1, 10, 1000) with no change.

Start by tracing where the liveblog_features filter is registered and applied in the plugin, then reproduce the report with the supplied WordPress filter callback and priority variations. Done means the filter callback runs and returning commands, emojis, and authors disables hashtags as reported.

Written by the indexing model from the issue text.