if you don't have anything positive to say about someone's post, it might be better not to say anything at all
Here is a great tip, also something you can use in your "live" day to day interactions/communication with "live" people; just think of the phrase "Just because it's in your head, it doesn't need to be said!"
This short pause as you become mindful, could prevent you from telling your spouse, "Yes those pants really make your ass look HUGE!", instead of maybe a more thoughtful answer such as, "They don't look as good as your red pants" (I know this can potentially lead to other problems, more questions etc) and you might even think of something brilliant like, "I think your 'no pants' look best."
SDG