This can be interpreted as summary of issues about the appearance and display of messages/conversations. Some suggestions are from other issues, some are from Gajim MUC. Concentrating all the ideas in one issue may provide a better overview. Additions are always welcome! The idea is to collect and integrate new issues/comments about chat appearance into this meta issue.

Chat

• Implement a switch to be able to change between simple / rich content display of conversations (old / new design)
• Display avatars of chat participants alongside each consecutive message, see #3724 (closed)
• Implement Consistent Color Generation (XEP-0392) for default avatars, see #9288 (closed)
• Optional: Display messages in speech bubbles, see #9052 (closed)
• Support Chat Markers XEP-0333, see #8163
• Highlight new incoming message text for x seconds, see #9351
• Indentation of multi-line messages, see #9052 (closed)
• Graphically highlight citations, see #9681
• Fix: Lock icon for encrypted messages looks bad with dark theme, see #8860 (closed)
• Fix: Lock icon for encrypted messages is copied along with chat messages on copy / paste, see #8860 (closed)
• Additional ability to copy plain message text without timestamp / nick (e.g. via context menu > copy message / copy text), see #3760 (closed)
• Add dark theme support in chat, see #8763 (closed)
• Add download option to link handling, see gajim-plugins#430 (closed)
• Display throbber / hint when syncing with MAM, see #8131
• Dynamically load history when scrolling to the top, #9683
• Display errors about messages not being sent near the associated message (e.g. tooltip), see #8527 (closed)
• Ability to change font size of messages via Ctrl + + / -, see #4468 (closed)
• Fix: Scrollbar breaks dialog when sending or receiving long links, see #8782 (closed)
• Fix: Dates for history are not calculated correctly, see #9272 (closed)
• Restored messages should be distinguishable from newly received ones

File transfers

• Inline display of file transfers (both Jingle / Http Upload), see #7583 and also #5671
• Preview icon for mime type of sent / received files (e.g. PDF, see gajim-plugins!188 (merged))

Commands

• Display a hovering listbox for possible nicknames of MUC occupants when pressing Tab, see #4653 (closed)
• Display a hovering listbox for possible commands when starting a message with /

[...]

To be continued.