LOCs were often published in letterzines so they formed part of the public back and forth. an LOC could also be a private letter mailed to the author or publisher - however many of those LOCs would be printed in the next issue of the zine for other readers to see and comment. A lot of this paper discussion took place before I entered fandom - it is only through the Fanlore and the Sandy Hereld memorial project that I've been able to access to and read some of these older zines. I entered fandom in the Usenet (and then mailing list) days of the early 1990s.