@vpador, it’s not really a bug in the sitemap generator but it’s probably just the author of that code didn’t declare his class methods ‘static’ and php is complaining in strict mode. The featured image warning didn’t seem that serious either. I think it’s just the IPB code is making errors that are otherwise invisible noticeable to you. It isn’t a conflict between the plugins. Hope this makes sense. If you turned on WP_DEBUG you’d notice a bunch more, even in the WP code itself. If you let the authors of the other plugins know, they’d probably fix those minor issues and the notices would disappear.
You could move the comments block
in class.ipbcomments.php around line 66, the register_comments method:
add_filter( 'comments_array', array($this,'show_forum_comments') );
above is the current hook/filter into the comments array, you could change that to appear somewhere else I guess. Look in the Codex for hooks/filters and maybe change ‘comments_array’ to something else.
You could extract custom postmeta and put the $topic_link somewhere else In your theme, maybe something like this: (untested)
<?php $meta = get_post_meta($post_ID,'forum_topic_url');
if ( ! empty($meta) ) : $topic_link = current($meta); ?>
<a href="<?php echo $topic_link; ?>">Follow the Discussion in Progress</a>
<?php endif; ?>
