I certainly don't. Here are my answers to Peter's questions, for what they are worth. Four months is an approximate time period, within which a letter to the editor commenting on an earlier publication would be considered timely.
Outright rejection is difficult to overcome, especially if no reason for rejection is given.
And many journals are edited by academics, whose bias is toward publishing academic research, and who establish academic standards for the research that they will publish. More and more these days, I think publication is designed to promote the careers of authors, instead of to provide accurate, important information to readers, and to the public. Scientific journals do not pay authors for the manuscripts they publish. About half of the major scientific journals have page charges, and about half have none. The best way to get an answer to this in any specific situation is to ask that particular author.