Note: Do not attach this concept to every issue page with a letter column.
Maintaining the tradition of science fiction magazines from the 1930s, as well as borrowing from the idea behind letters to the editor at newspapers, comic books in the 1940s started a tradition of letter columns, in which fans and readers could write into the editors and ask questions or give their opinions. Early letter columns reflected the target audience of comics at the time which was primarily children and letter columns had a respective focus on children's questions about comics.
With the expansion of the medium in the 1960s away from the traditional model aimed only at children, the level of analysis and interaction in the letter columns increased. This was so much the case in the 1960s that some letter columns had to expand to a second page to handle the letters (as was the case with Peter Sanderson's lengthy letters.) As there were primarily two main companies at the time (DC and Marvel) the letter columns for each company varied in their approach. DC generally featured letters in which characters were requested for the titles. Marvel on the other hand generally included letters which critiqued the series in question (and was willing to print negative criticisms.)
Due to the the offset in reading and publishing, it was common for letters to deal with issues that were 3 to 5 issues past. As well letter columns were well known for publishing the addresses of comic fans, in which other comic fans would write letters to those that they had read. At the height of their popularity it became a sign of accomplishment for a fan to have a letter published. Both DC and Marvel at different times had series that could not garner enough interest and thus letter columns would occasional receive requests for fans to write in, and barring that, employees for the two companies might write letters to appear as though were from fans.
The term letterhack came to be used by some to refer to the fans who would constantly write to letter columns. Some notable letterhacks include Peter Sanderson, Irene Vartanoff, Bob Rozakis, Kurt Busiek, Mary Jo Duffy, Mike Friedrich, Mark Gruenwald, Fred Hembeck, Tony Isabella, Paul Levitz, Ralph Macchio, Martin Pasko, Diana Schutz, Beau Smith, Roy Thomas and Kim Thompson.
One of the most famous letterhacks was Canadian comics fan Jim Burke, who wrote in excess of 3,000 letters to comic book letters columns between 1977 and 1994 under the pseudonym 'T.M. Maple'.
Interactive Reader Decisions - Occasionally through the letter columns or other means the creative teams will let the readers directly choose an outcome for the characters in the series.
Reader Submitted Fashion - As opposed to letters, in these cases readers submit pictures of their favourite characters wearing fashions which they have designed.
Romance Comics Romantic Advice - During the height of the era of romance comics, it was common that an advice column existed within each issue where romantic advice could be given to readers.
Showcase - The 1960s series Showcase started off on the provision of providing fans what they wanted, and although it deviated away from this format relatively quickly, the first issue displayed that it had been conceived with the idea of fans writing in to say what kind of adventures they wanted to see.
The 1980s The Question series had suggestions for readers to follow on the philosophical concepts put forward in the book.
In the 1980s and 1990s, the US Postal Service had issues with delivering letters for the Suicide Squad letter column, as the name of the column was "Suicide Notes".