Guild Wars 2

When the trait Shrug it Off triggers its “free” Shake it Off, does that count as a shout when it comes to Soldier runes and the Vigorous Shouts trait (shouts heal) ?

Yes, it counts as a shout. Condi remove x2 and heal ofc.

However, it activates upon getting the first stack. If something gives you say 5 stacks of vulnerability, the trait will activate upon getting the first stack, removing only one, but ideally the shout condition removal will take care of the rest, still annoying though.