That's a feature, not a bug. If you're dead but haven't respawned yet due to lag, the server doesn't let you place any blocks, and other players will see you frozen at your spawn point. I think it's better than when sometime you would kill someone, and their connection was terrible so you'd have to keep avoiding them for 5 seconds until they actually respawned.
You can still get posthumous kills, as long as you place the TNT before you die and the purple block after. If everyone like the lag glitch, maybe allowing you to place purple blocks in the spawn to explode would be a good compromise?
You can still get posthumous kills, as long as you place the TNT before you die and the purple block after. If everyone like the lag glitch, maybe allowing you to place purple blocks in the spawn to explode would be a good compromise?