SEDNA offers many ways for teams to communicate and collaborate, including the ability to tag colleagues and comment on messages.
In SEDNA there are both outbound (sent) messages and inbound (received) messages. If Team A sends a message to Team B, the message on Team A's end will be outbound while for Team B it is inbound. While the messages have the same content, they are different and distinct, including different message IDs.
If there's a message where your colleague sees comments and you don't or vice versa, please ensure that you're both looking at the same version of the message, inbound or outbound. You can verify this by comparing the message IDs or checking for the paper airplane icon in the message list, which only appears on outbound messages.
If you are not viewing the same version of the message, first check if your team has access to the version on which the comments appear. Should you not have access to that version, the message can be shared with your team to grant you access.