Our trade deadline just passed and I see four teams immediately sent anywhere from 10-37 players to the waiver wire; some guys are studs, some are end-of-the-bench at best. I assume these are revocable waivers and they do they so they can "offer" them now and then potentially trade them later in the season without fear of actually losing them, is that correct?
Is there some unwritten code that you don't claim these guys?

Correct, pass them through waivers, then pull them back (revocable), maybe/maybe not negotiate with the claiming franchise.

Nope, put in waiver claims; if for no other reason than to prevent them clearing waivers or a better team getting better

No unwritten code. There are many reasons to place even the best players on revocable waivers; I do it mainly to allow for roster flexibility at the end of the season and going into next season. But I don't have to tell anyone my reasons. So you don't have to tell anyone your reasons for claiming anyone you want. Yes, sometimes there is someone trying to put a legitimate late trade through, and it's entirely fair game to block it whether you mean to or not.

funny...in real MLB there used to be such an unwritten code that all GMs would pass their roster thru waivers, essentially extending the trade deadline. Then came the Theo-type analytical GMs who willingly broke the unwritten code, if for no other reason than other contending teams wouldn't be able to add late. Nowadays only bad contracts get thru waivers.

Sometimes I waive them all some times I do not. If I am wanting to make a move on a player I will waive them. If I have a player I want gone next season I have waived them with out revoking and have gotten lucky when someone got them.

If I recall, it was specifically Brian Cashman who broke the unwritten rule and started the trend...not to say it didn't need to be broken.

Sometimes I do it, sometimes I don't. I don't waive anyone I intend to keep just on the off chance I forget to click the revokable box, lol. Same reason if there's someone I want I'll put a claim in for, even if I have no interest in trading for him. Maybe someone waived the player outright.

Had a guy in one world say in world chat "don't forget to waive your guys so you can trade them later." Hey, I'll do whatever I want, cha cha.