Problems with forum posting editor

Question

Many times that I use any text formatting or (not sure what), when I try to preview or post the reply, I get error:
Your post has been changed because invalid HTML was found in the message body. The invalid HTML has been removed. Please review the message and submit the message when you are satisfied.
Can anyone confirm they've seen the same issue?
Where should this bug report be directed?
When that error msg appears, nothing is ever been removed.  The same text formatting & all content are the same, but it still doesn't allow submitting or previewing it.
It also doesn't highlight the errors,so they can be corrected.  Just lets you guess.
When previewing or submitting this post, it gave the error.  The 1st time, I found an extra blank line (a blank line?).  Removed it, then I could submit.
To further test, I added basic formatting (bold, italics) & changed color of a word.  Once, it accepted that.  Another time, it didn't.
I removed all that formatting (by most editors' process) - still didn't like it.
Found it was the text color.  It was removed on the page, but still a problem.  I deleted the word & re-typed (no color).  It accepted it.  Takes too much time guessing - like a blank line.
If it requires plain text - OK.  Just remove the wysiwyg & don't allow any imported / pasted content to be anything but plain text (remove all formatting).
I don't have this problem on any other forum that I remember.  Thanks.

Answer 1

Thanks, but nope - it's too inconsistent.  Very.  In the same post / reply, within a few min. span, or different days & posts or replys.  Doubt that's related to moving up ranks? 
Besides, how long do you have to be a member, how many posts, etc., before it allows using HTML, that 90+% of all forums allow the 1st day?
It's too much trouble, just to see Preview (no other forums work like this).  Just because I accidentally hit Return twice?
I'd rather ditch rich text - but don't seem to be able. 
I turned it off in CP settings & saved (it's still disabled in settings, after logout & login).
Logged out, closed page / tab.
Cleared all cookies, cache, etc.
Logged back in.  Rich text still showing in the Post or Reply editor, though is still disabled in CP.
Most every forum will remove extra blank lines, spaces (if doesn't like them) - not force users to review every space. 
If formatting (any) doesn't work, or if user hasn't achieve proper rank, just disable formatting toolbar.
Thanks.