As Brian said, these are mailboxes (or System Wide Folder - they too have a leading 2).

The local mailbox normally will look like this

2,1,"203A1978:My Mailbox","","My Mailbox"

and normaly there will be entries for folders in the local mailbox starting with a leading 0 and pointing to "203A1978:My Mailbox". Be sure your entries are not for the local mailbox (have a look at STATE.PMJ -> Mailbox_IDs -> Default)

I assume you use IMAP and you named the IMAP-Mailbox "Davis". I don't know why or under which circumstances those entries are generated for the same mailbox (folders hierarchy of IMAP-mailboxes will not be saved in HIERARCH.PM) and I have one IMAP-Mailbox that has only one of those entries - but the others have hundreds. I remember that I deleted those entries (on closed Pegasus) some years ago ... but they come up again over the time :-)

Cheers    Olaf

Time to clean up this file (after ~10 years of use of pmail).

I find about 300 lines in the file with this general form

 2,0,"689B6962:1e7bde1801348ab5","","Davis"

The number before the colon can change, but hundreds have the 1e7bd.... identifier (and "Davis" is of course me).

What are these, and are they safe to delete? (I can't find any files or folders with anything like these names, while I can easily find the FOLxxxxx files).

thanks in advance

The entry starts with a "2" which indicates it is an entry for a mailbox.  Do you use an IMAP profile named "Davis" or add a directory named "Davis" as an added mailbox?

As for whether they're safe to delete, probably, but I'm not recommending it.  Too many failed attempts at "cleaning up" HIERARCH have changed my thinking from keeping it lean to not fixing it if it's not broken.