I think public comments on the internet basically should consist mostly of arguments, and therefore be highly negative (although obviously not any old negativity-spreading post is good).
A useful standard for communication in general is that some message you send (be it on a forum, face-to-face, the front page of the New York Times or whatever) should (at least) be informative or important. An informative message would be one that contains some idea that the audience is not already familiar with; an important message would be one that the audience has some reason to care about even if the ideas in it are familiar. In public commentary, simple agreement will usually fail on both counts. If you agree with somebody, that basically means your ideas are similar to theirs, so it's not likely agreement will make for an informative post. And being a public comment, most of the audience are functionally strangers to you and it is probably not important to them whether you personally agree with them (note that this point doesn't apply well to private or personal communications as a lot of people would think it's important to know whether their friends/family/etc agree with them about some topics).
I bring this up because the structures of most social media websites seem to promote disagreements which are uninformative and unimportant, and in combination with the prevalence of social media and the fact that it's basically unpleasant when somebody disagrees with you I think this has resulted in an unwarranted prejudice against disagreements in general.
Furthermore I think the internet has a comparative advantage as an environment for disagreements, meaning that if you are going to have a disagreement with someone it is better to have it online than in some other environment. I could make a lot of long arguments for this point but probably the simplest convincing reason I have is that it is more difficult to escalate an online disagreement with a stranger to violence than it would be if you were just physically talking to that person, since in the latter case you always have your fists. Since internet comments don't seem to have comparative advantage in much of anything else (at least nothing as widespread as disagreements are), this in combination with the usual facts about comparative advantage suggest that most internet comments should be about disagreements and many (not all and probably not even most) disagreements should happen through internet comments. Note that this doesn't extend to all forms of internet comment; Twitch chat, for example, is a pretty bad place to have a disagreement, as are many social media websites. But if you website isn't good at hosting disagreements it's giving up one of the key advantages of the internet and many websites which are not good for disagreements seem to me like they do not make up for it and simply should not be used.
Or, for a ruder way of putting all this: it's not actually a problem that people online are mad at each other all the time, even for those people. If you don't like that, go outside, or talk to your friends, or read Epictetus, or try yoga, or...
Geez, that sucks. I have a similar problem in my room back in my hometown pretty much every rainy season. The other side of one of my walls is in the outside and completely unprotected, and since my house is located in the second floor it's not exactly trivial to clad or paint it. It always gets wet and attracts mold. I've had to sleep in the couch in the living room several nights waiting for the rain to stop and my wall to dry so I could solve the problem. It turns out breathing in mold while you sleep is pretty damn terrible for your throat and lungs (I've gotten sick several times because of it).