Toxic comments can be just as common in non-anonymous forums and venues. Facebook produces a lot of toxicity, for example. Further consider; the Internet is much less anonymous then twenty years ago and that hasn't stopped the overall level of toxicity imo. The type of person who spontaneously makes toxic comments spontaneously will still make them when forced to use their real name (they'll just suffer more from it). The provocateur, those who calculatedly elicit toxicity, is always going to be here too - no matter many Russians Facebook filters.

One factor is that once one person begins attack another person, both using real names, both people have a hard time backing down, especially if they know each in real life or if they are semi-public figures. For a lot of people, admitting that they are wrong is a huge hurdle - and these tend to be the people who engage in toxicity in the first place.