Confirmed same in 1.15.2
confirmed 1.14
Can confirm I have major input lag with issue going worse with lower fps
My java version:
openjdk 10.0.1 2018-04-17
OpenJDK Runtime Environment (build 10.0.1+10-Ubuntu-3ubuntu1)
OpenJDK 64-Bit Server VM (build 10.0.1+10-Ubuntu-3ubuntu1, mixed mode)
This also happens to me too. I get duplicate key registers for the open chat key and open command key. Changing the open command key to the keypad 1 key results in "/1". This issue only ever happens when opening the chat buffer and not while its open. I've only had this issue with 1.13 snapshots and no other version of minecraft or any other program for that matter.
Confirmed in 20w30a