This was something that Agama had mentioned before, but I never experienced it myself. Agama and Surb just tested this to make sure and they said that it does cause lag.

If you have shield or strength and someone specs you, it causes lag.

This is on a 2.4.2 server with both 2.4.2 and latest SVN clients.

Some others may want to test it also and see if they experience the same.

To recreate:

1. Get two players
2. Player1 joins a server and Player2 joins as a spectator (but Player2 is not spectating Player1 yet)
3. Player1 grabs strength or shield and runs around for a few seconds to make sure they are not choppy.
4. Player2 starts speccing Player1
5. Player1 starts experiencing choppiness
6. strength/shield expires and Player1 no longer experiences choppiness.

I think I have experienced this at some time, I have not actually tested it though. I often experience choppiness with strength/shield though just in general.

I usually get choppiness with strength while being not speced. Yet I think that you can partially see the globe surrounding you and this cause rendering lag.

I've experience this in play, not just specing.

Sounds interesting I will try this.

Okay. I tried this on my listen server (SVN) and a public server (2.4.2) with ai.
And yes. When I have strength and when he starts to specc me I start to get a little choppy. Walking up stairs is most noticeable but also just walking forward + turning left or right.

I find it strange that a spectator can influence my movement. But indeed this seems confirmed for me.

cl_movement 0 is not affected by this in my tests.

[theory!]
I felt a bit slower (when I had strength + spectator) and THAT may be the cause of the misprediction with cl_movement 1.
But my speedmeter showed 37 km/h when walking a straight line. With and Without strength + spectator. So that may bust this theory.
[/theory!]

It can't be ONLY spectator thing cause I get choppiness with strength (and maybe shield) in public CTF most of the times. It can't be that I'm spectated all the time.

Obvious, strength has a realtime light effect. That's what's taking effects and causing choppiness.

After div0's fix in SVN it seems to be fixed!
I can't reproduce the choppyness anymore.