Update avatar also updates per room display name

[mikafinja]

Description

Setting a new avatar via /_matrix/client/v3/profile/{userId}/avatar_url also changes the per room display name in all rooms to the display name set in the user's profile.

Steps to reproduce

• in at least one room set a different display name with /myroomnick nickname for example with element or element web
• go the your profile settings
• set only a new avatar
• click save

expected behavior:
The avatar and only the avatar is updated in all rooms

what actually happens:
Room specific display names are also updated to the display name configured in your user profile

Homeserver

https://matrix.ccc-ffm.de

Synapse Version

1.88.0

Installation Method

Debian packages from packages.matrix.org

Database

PostgreSQL

Workers

Single process

Platform

Debian 11, virtual machine

Configuration

nope

Relevant log output

no relevant logs created

Anything else that would be useful to know?

The client only sends a request to update the avatar but the server also updates the display name.

The only request send is the following put request: /_matrix/client/v3/profile/{userId}/avatar_url as specified in https://spec.matrix.org/v1.7/client-server-api/#put_matrixclientv3profileuseridavatar_url

[erikjohnston]

In general the semantics of display names/avatars is a bit of a mess, and per-room profiles are more of an accidental feature than anything else. I think we'd accept patches for this particular case, but I don't think we care enough to consider it a defect per se.