No, I don't tag players at the poker table. They can change their style of play. I try to get information while playing.
I saw on twitch a guy playing on ignition using HUD. Is that allowed?
You can use HUD on Bovada\Ignition Casino. It would only keep opponent stats during a session on cash game table or during an individual tournaments. The HUD retain cumulative stats only for your play.
The HUD is best used to review your own play.
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I do keep player notes via the site or in HUD.