I noticed, that when you type a command and let it get completed, the suggestions are not really "logged" in the chat but still take space
I think this is a new bugged feature, so I guess that the suggestion goes away is intended
How to reproduce:
1. Bug:
Type in the chat some words like "Hi" and press ENTER
Type "/give @p minecraft:" and press TAB and then ESC
Now open the chat and scroll up, you will still see the suggestions
Now type "/g" and press TAB
The suggestions are away (which is pretty usefuly), but they still took space. You can see that when you open the chat and try to scroll to your "Hi", you won't find and it seems like you just started typing, so only 2 lines are occupied
2. Bug:
Type in the chat some words like "Hi" and press ENTER
Type "/give @p minecraft:" and press TAB and then ENTER
Now open the chat and scroll up, you will still see the suggestions
Now type "/g" and press TAB
The suggestions are away, but only after you used the suggestion again, it should rather go away when you press ENTER or when you close the chat with ESC
Confirmed in single player survival. I searched the bug reports and did not find any with this specific complaint, but please forgive me if it is there and I missed it. It does seem that you chat history gets erased with tab completion of "/give @p minecraft:"