This issue is interesting for a number of reasons. It’s somewhat of a precursor to Loki’s attack on Sif’s hair— seriously, bro, is this a habit or something?—and it clearly outlines his motives.
He’s jealous of Glimda because Thor compliments her excessively and she receives positive attention from most of Asgard, so of course the only thing he can do is chop off what apparently makes her better than him in Thor’s eyes: her hair. “No longer will she be showered with compliments which are rightfully mine”? Seriously?
Also: I love the little detail that Loki and Thor did, in fact, share rooms into their teen years. It’s usually regarded as fanon, but scenes like this show otherwise.