Slack has listened to feedback and given us a way to toggle off the sidebar avatars.

(This only seems to be available in the Beta channel at the moment)

Display or hide profile photos

1. From your desktop, click your profile picture in the top right.
2. Select Preferences from the menu.
3. Click Sidebar in the left-side column.
4. Check or uncheck the boxes next to Show profile photos next to DMs.

View previous instructions

1. Message yourself /slackdevtools
2. In the DevTools console:

function addStyle (styleString) {
  const style = document.createElement('style');
  style.textContent = styleString;
  document.head.append(style);
}

addStyle(`
  .p-channel_sidebar__presence_icon.p-channel_sidebar__presence_icon--on-avatar {
    transform: scale(1.5) translateX(-6px) translateY(-5px);
  }

  .p-channel_sidebar__mpim_counter {
    transform: scale(1.2) translateX(-4px) translateY(-4px);
  }

  span.p-channel_sidebar__mpim_avatars_mpim1.c-avatar {
    opacity: 0;
  }

  .p-channel_sidebar__channel span.c-avatar {
    opacity: 0;
  }

  .p-channel_sidebar__user_avatar--hide-presence .p-channel_sidebar__presence_icon--on-avatar {
    display: block;
    transform: scale(1.5) translateX(-3.5px) translateY(-9px);
  }
`);