What to put in comments of a report?

Today has got to be the worst day of League that I've experienced to date. Back to back games with teammates flaming me for not ganking them specifically or for any little mistake (for example red being stolen by a Kai'sa W, and being flamed in all chat by my adc/support duo for it). If this was ranked I wouldn't even be surprised, I go into ranked expecting this type of thing, but this is the first time I've seen so much toxicity in normals. Obviously I've had to put in a ton of reports today.

So my question is, what should you put in the comments section of the report? Does it even matter if you fill it out?