@simontatham @nicksilkey, hmm…

$ echo -n foo | xclip -selection primary -loop 1 -verbose
Loops: 1
Using selection: XA_PRIMARY
Using target: UTF8_STRING.
Waiting for one selection request.
    + Creating new requestor for 'Easy Effects' (0x2600002)
    - Deleting requestor for 'Easy Effects' (0x2600002)
$

… er, what? Okay, if it were Clipman, that'd be fine (that's expected), but Easy Effects?

(It does this to XA_CLIPBOARD too, but not XA_SECONDARY. Running 7.2.3; I don't know if 8.x does this.)