We now have a new filter widget_text_content
introduced in 4.8 src, with the following default callbacks:
add_filter( 'widget_text_content', 'capital_P_dangit', 11 );
add_filter( 'widget_text_content', 'wptexturize' );
add_filter( 'widget_text_content', 'convert_smilies', 20 );
add_filter( 'widget_text_content', 'wpautop' );
that are applied if the filter settings, for the widget instance, is set to 'content'
.
When you remove the filter settings by hand from the wp_options
table, it seems to be reset during the update method src.
See trac ticket #35243 for more info.