There has been a legitimate concern about board clutter in the past, and the primary reason for a rule against it is to keep research easy and simple, especially when there are multiple threads on the same SP or agency. However some topics have bedeviled the moderators, particularly those on the subjects of racism/bias and STDs. In the past, these threads were sometimes started with a specific agenda to tarnish a specific SP or agency. Other racism threads appeared to be based on ordinary miscommunication or conduct that the average fair minded person would not consider necessarily racism or bias but conduct attributable to other factors. Threads on STDs were started by persons who were not medical professionals posting theories or conclusions simply not backed by any credible scientific evidence, and the Mods had to shut them down as bullshit.
There are some topics where duplication of an old thread isn't necessarily a bad thing. I started a restaurant thread which was inactive for a while and then Panthere started another one. This was not really an issue because restaurant reviews are generally stale after 6 months anyway. If Panthere's thread is inactive for 6 or more months there should not be any objection to shutting it down and stockpiling or deleting it in favor of fresh reviews.
In the case of this thread, the main argument to leave it open and junk the BookerL thread is that the BooklerL thread spawned no comments or discussion. Therefore there was nothing in it that was duplicative, assuming someone researching the topic could actually find it. Unfortunately BookerL, although he has started a number of threads, does not always give them user-friendly or research-friendly titles, perhaps in part because French is his mother tongue and English is not. I don't know why- but many times, and not just with BookerL's threads, threads are started with titles that do not really indicate what exactly is under discussion, and this results in board clutter when nobody researching that topic can find the already started thread.
Over the years, the Moderators have at various times tried to drill down to members these various points, with only occasional success. They are usually hampered by newer members who simply come on the board half-cocked and don't do any research and assume they can start a discussion on anything. Some of the Mods have become very inflamed and irritated by such threads, and who can really blame them.