That’s odd. I’ve tested it with pages, not posts, and when a single page is updated, only that one page is marked for rebuild or deleted–the rest of the cache remains intact.
Glad it helped a bit at least.
I don’t think the whole else block should be commented out, just that line (the other line in there deletes the single post’s cache).
FWIW, I believe the problem is in wp-cache-phase2.php, line 1079:
if ( isset( $GLOBALS[ 'wp_super_cache_debug' ] ) && $GLOBALS[ 'wp_super_cache_debug' ] ) wp_cache_debug( "wp_cache_post_id_gc clearing cached index files in $dir.", 4 );
//prune_super_cache( $dir, true, true );//Comment out this line to prevent all cached files being deleted when a single post id updated
I’ve commented out that line as indicated above and now only my edited page is deleted/rebuilt. All other cache files remain intact.
