So maybe Loki's grip on the reins tightened a little, and he was also, quite definitely, Sitting Back In The Saddle, although not so far for it to be a signal to back up.
He didn't, actually, want the horse to walk backwards.
And then he was busy making happy soothing-the-horse noises, talking calmly, in ... Westminster Latin ... wait.
Well, maybe Jotnar was the only one who understood what he was saying, but at least the tone doubtless made sense to Katie! And, hopefully, soothed her out of her sulking.
And then Loki looked back up at Sif, remembered to speak in English, and completely neglected his previous point to ask: "My instinctive assumption is that you're putting me through my paces, by which experience I'll get to judge hers - so tell me, Madam Equestrienne, shall we walk, to start?"