There's a fair bit of advice here: Right Speech
The detailed meaning of some of that might be not-entirely-obvious at first reading -- for example:
"Not lying" probably includes, beware of telling jokes if they're untrue, ditto exaggerating.
Sarcasm and exaggeration are difficult, maybe especially online.
If you must use them then, I'd say, always add an emoticon, to telegraph they're untrue -- because otherwise I might suffer in ignorance without getting the joke
I think it's a context which sees emotional afflictions such as anger or hatred as a fetter, a hindrance.
And, "a sense of the proper time for saying them", is not necessarily, "whenever I feel like it, damn it!"
Additionally I find this -- The Insult -- rather magnificent. It's about not getting involved, even if somebody is trying to be insulting (and let alone when they're not).
I read Wikipedia's Emotional labor article today. I don't entirely buy-in to the concept that there is such a thing, but it's a theory, a description. Note what it says about "surface" and "deep" acting, e.g. re. Physicians:
Overall, Larson and Yao (2005) argue that physicians are more effective and enjoy more professional satisfaction when they engage in empathy through deep acting due to emotional labor.
That slightly contradicts the "even when you don't want to" in the title -- i.e. perhaps you should want to. If I don't want to be nice then instead I try to post nothing at all -- that's one of the benefits of this medium, i.e. it's not real-time, you can take a break, have second thoughts before you write something.
On the subject of emotion, I've read some claim that according to Buddhist doctrine there are four emotions recommended as being appropriate for all social interactions. The four are, three different kinds of love ...
- I hope you're well
- I don't want to hurt you
- I admire/approve your doing well
... plus, equanimity as the fourth.
I met a young Friend (i.e. a teen Quaker) when I was young, who said, "I'll discuss anything with anyone, but if it turns into an argument I walk away." Memorable.
What else. This one -- Punna Sutta -- is kind of interesting:
“The people of Sunāparanta are wild and rough, Puṇṇa. If they abuse and insult you, what will you think of them?”
“If they abuse and insult me, I will think: ‘These people of Sunāparanta are gracious, truly gracious, since they don’t hit me with their fists.’ That’s what I’ll think, Blessed One. That’s what I’ll think, Holy One.”
“But if they do hit you with their fists, what will you think of them then?”
“If they hit me with their fists, I’ll think: ‘These people of Sunāparanta are gracious, truly gracious, since they don’t throw stones at me.’ That’s what I’ll think, Blessed One. That’s what I’ll think, Holy One.”
“But if they do throw stones at you ... (etc.)
"Sticks and stones". So you might want to see the person you're talking with as being "gracious, truly gracious" (sometimes translated as "civilised, very civilised").
There's one more bit I'd like to recommend -- Ursula K. Le Guin -- Bryn Mawr Commencement Address (1986).
Le Guin is -- was now -- a famous author. She knows words. Anyway, this "commencement address" is quite long, but was new to me when I read it and worth knowing.
It starts by talking about different modes of speech, which she calls the "father tongue" and "mother tongue".
She warns that we'll be inclined to use the father tongue (for public discourse) but that's maybe inappropriate -- it distances, it talks down, it thinks it's the voice of reason ...
And it is indeed an excellent dialect. Newton's Principia was written in it in Latin, and Descartes wrote Latin and French in it, establishing some of its basic vocabulary, and Kant wrote German in it, and Marx, Darwin, Freud, Boas, Foucault - all the great scientists and social thinkers wrote it. It is the language of thought that seeks objectivity.
I do not say it is the language of rational thought. Reason is a faculty far larger than mere objective thought. When either the political or the scientific discourse announces itself as the voice of reason, it is playing God, and should be spanked and stood in the corner. The essential gesture of the father tongue is not reasoning but distancing-making ... (etc)
It takes detours, into poetry, and feminism.
There's a bit here I'd like to quote:
If I try to be objective I will say, "This is higher and that is lower," I'll make a commencement speech about being successful in the battle of life, I'll lie to you; and I don't want to.
Early this spring I met a musician, the composer Pauline Oliveros, a beautiful woman like a grey rock in a streambed; and to a group of us, women, who were beginning to quarrel over theories in abstract, objective language - and I with my splendid Eastern-women's-college training in the father tongue was in the thick of the fight and going for the kill - to us, Pauline, who is sparing with words, said after clearing her throat, "Offer your experience as your truth." There was a short silence. When we started talking again, we didn't talk objectively, and we didn't fight. We went back to feeling our way into ideas, using the whole intellect not half of it, talking with one another, which involves listening. We tried to offer our experience to one another. Not claiming something: offering something.
That ties in with using "I-messages" as a deescalation technique.
If I say, "X is true!", then you might think, "It's only true sometimes", or, "It's not true this time", and you might reply, "No it's not!", and then, we're arguing.
If I say, "I feel X!", then I think you're less likely to reply e.g., "No you don't!"
And so, an "I message" might be easier to hear and to accept.
Anyway -- good luck!