The answer is: No.
If you post a message in a Messge Room, and then you remove that message, then it is impossible for any Upwork user who is part of the message room to see the messgage in the Upwork Messages tool.
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The answer is: Yes.
If you post a message in an Upwork Message Room, then the message may (or may not) be relayed to the other participants in the thread using Upwork message relay. This means that if the user is not actively using the Upwork Messages tool, the messages posted there by others may be sent to him via email. So even if you deleted a message, the message may be in the email inboxes of the other participants of the message. You don't know for sure if the message was relayed to them via email, but it is safer to assume that it WAS relayed to them.
ALSO: If you post a message in the Upwork Messages tool, it is possible for the other participants in the room to copy the message and paste it into a text file. Or onto their blog. If they are being observant, then you can post a message, they can copy it, and then you can delete the message two seconds later. But in th short time that the message was visible, they could have copied the message and posted it to Instagram. Is this likely to happen? No. Is it possible? Yes.
