Typing text is super laggy

Verification builds: 1.2.10 (662590) & 1.2.11 (686814)

Summary: Typing commands, chat text or editing command blocks is very laggy. The text buffer appears to fill on key press, but rendering in the game client is extremely slow. This can be quite frustrating editing commands, especially when you need to delete characters and are unsure if the game is still processing input.

Impact: Laggy text I/O

Repro Steps:

1. Type (fast)
2. Observe slowness

Observed Results: Typing at a slow speed is generally okay, typing a regular command at a decent typing speed will almost always be laggy.

Expected Results: The game shouldn't have laggy input, several iterations ago this was not an issue.

Screenshots/Videos attached: https://youtu.be/8yra47IyAcU?t=28 (microphone on and hitting keys hard!)