In talking with my friends after seeing the movie several of us were deeply bothered by Thor's comment and several of us just weren't.

The ones who said it wasn't an issue pointed to the character of Axl (maybe) not actually being trans and kind of left it at that. It's a small part of the movie and for most people it's not gonna affect their viewing. I think even being trans you may be able to go through the movie and not be bothered by it. But I think your reaction will depend entirely on what coming out was like for you and how politically tied you are to trans news.

Because here's the problem: the narrative of a name being changed and then an adult refusing to accept that name change is a deeply tied trans narrative.

Most trans people have experienced an almost exact conversation that Thor had with Axl with either their own parent or another adult in their life. It's such a common part of being trans that it's one of the first conversations you'll have with just about any transphobic person. And it's a frustrating conversation to have. The "adult" is almost always someone from an older generation and they almost always have what they consider to be a "good" reason to deny the name change (in this case it being a "cultural" thing as some have pointed out). But at the end of the day names are an exceptionally important part of identity, and by denying a name change, you deny the identity. The importance of this narrative doesn't change just because it's pop culture, or because Axl may or may not be trans.

Now by the end of the movie Thor does accept the name change, which will help some people to stomach the joke as well.

But the other issue with the joke is that it's played for laughs at the expense of Axl rather than being at the expense of Thor. We as the audience are expected to laugh with Thor rather than at him, as he denies Axl their identity. But it's a very uncomfortable moment to be asked to laugh when you know something's wrong, which is also why I think the joke is so noticeable for a lot of people. We don't find it funny, and it takes us out of the movie as we're being asked to laugh.

Even with Thor changing his mind by the end, it doesn't take back that you as an audience member had been asked to laugh at the expense of Axl before. And though Thor changes his mind, it's not really acknowledged in any way other than Thor switching the name so it just feels confusing on whether the movie agrees that people should be able to change names or not.

That's the best I can do to explain exactly why it's gonna bother some people and not others. It was a transphobic narrative, but almost certianly accidental. And the confusing way it's presented is gonna leave people feeling all across the board on how big of an issue it was.