A limit of right speech At what point does the discussion of others become wrong speech?

"Abandoning divisive speech he abstains from divisive speech. What he has heard here he does not tell there to break those people apart from these people here. What he has heard there he does not tell here to break these people apart from those people there. Thus reconciling those who have broken apart or cementing those who are united, he loves concord, delights in concord, enjoys concord, speaks things that create concord."

Being that I am not an arahat, I need to work through occurrences, sometimes my mind is not enough, so doing so with other people could be helpful. But to talk through some events by those committing wrong speech, wrong action - with those that one considers capable of adding something positive - necessitates their exposition as wrong speakers etc, so is certainly close to creating rifts. 

I understand that the above has right intention - no desire to spread rumours or damage others' opinion of others, but how to decide whether it is wrong speech?

I suppose choosing a person that is not easily susceptible to jumping on disconcord, that differentiates between direct and indirect experience, and that aims to solve problems is a start, but is there anything from the texts?
From Abhaya sutta:


  [1] In the case of words that the Tathagata knows to be unfactual,
  untrue, unbeneficial (or: not connected with the goal), unendearing &amp;
  disagreeable to others, he does not say them.
  
  [2] In the case of words that the Tathagata knows to be factual, true,
  unbeneficial, unendearing &amp; disagreeable to others, he does not say
  them.
  
  [3] In the case of words that the Tathagata knows to be factual, true,
  beneficial, but unendearing &amp; disagreeable to others, he has a sense
  of the proper time for saying them.
  
  [4] In the case of words that the Tathagata knows to be unfactual,
  untrue, unbeneficial, but endearing &amp; agreeable to others, he does not
  say them.
  
  [5] In the case of words that the Tathagata knows to be factual, true,
  unbeneficial, but endearing &amp; agreeable to others, he does not say
  them.
  
  [6] In the case of words that the Tathagata knows to be factual, true,
  beneficial, and endearing &amp; agreeable to others, he has a sense of the
  proper time for saying them. Why is that? Because the Tathagata has
  sympathy for living beings."


https://www.accesstoinsight.org/tipitaka/mn/mn.058.than.html

This sutta is also interesting, because it suggests that being silent can sometimes be wrong speech in a sense. There may be situations where we need to speak up to prevent harm. Right speech then becomes a question of knowing when to remain silent and when to speak up. Timing becomes a factor.

What is considered factual, true, beneficial, endearing &amp; agreeable, and not least proper timing will probably always be subjective to a certain degree, so it's hard to draw a clean cut line between right/wrong speech. One will always need be mindful to make good judgements, i suppose.