Intention behind Queer representation, does it matter?

Yes, but that's the short answer.

Many readers are able to identify the author's intentions behind the queer representation in their work. The readers will notice if the author understands or did research about a certain identity, if they used outdated stereotypes, or if they treated their queer character as real and complex as the rest of the cast. The readers will wonder things like: Did the author cut corners about this queer plot line? did the author consider the social context of queer people in different environments?, etc. The intention behind the queer representation in a piece of work can affect the work itself as well as the readers' perception of said work.

Of course, I'm not saying this to scare you off portraying queer people and experiences in your work. I just want to remark the importance of treating queer characters and experiences with care because other people will read your work. There is enough portrayal of queer people that feels like a mockery or feels as if the author wasn't informed enough about the topic, why add your work to that pile?

But let's say it was not the author's intention to convey a queer character or experience. Maybe a fantasy or space sci-fi character has aspects or goes through experiences that resonates with queer people (this happens more than you think for cool reasons but that's another topic). Even if it was an accident, now the author has a queer-coded character in their hands.

As you have probably noticed, intention doesn't matter too much in this specific case, but your reaction does take it's place. If the queer representation wasn't intentional don't shut down your audience! The best thing to do its to accept it and move on. You may have not thought about your character as queer but does it really make any harm? The new perspective invites more people to read your work, engage with it and even start analysis about your work in a different light! It's a win-win situation.

Intentional or not, remember that your work will be out there for many people to read. Some of them will be queer. Make sure to remember them when writing about them!