I couldn't find an answer to this (perhaps because I'm overthinking this), but does Vorel of the Hull Clade's ability count as "putting" counters.
For example: If you had Corpsejack Menace out, and you targeted a creature with 4 +1/+1 counters with Vorel's ability, would you then you then put 8 additional counters on it? My assumption would be 'yes' based on 701.9e, but I figured I'd double check.
701.9e To double the number of a kind of counters on a player or permanent, give that player or permanent as many of those counters as that player or permanent already has.
As far as the rules are concerned, putting counters on an object includes—
"putting counters on that object while it's on the battlefield", regardless of what verb is used to refer to that action (whether "put", "move" [C.R. 122.5], "double" [C.R. 701.9e], "give", or some other verb), and
the case of "an object that's given counters as it enters the battlefield" (e.g., "enters the battlefield with ... counters")
(C.R. 122.6). If what is now C.R. 122.6 doesn't clarify this enough for you, it's up to the rules manager to.
EDIT (Jul. 26): Edited generally, including because one rule was renumbered in the meantime.