People about Cosplay...
When judging whether something is cultural appropriation, ask first: is there a cultural double standard that praises the borrower while punishing those whose behaviors/styles are being borrowed from? If not, then the second test is to see if the thing being borrowed has religious/spiritual/historical significance the borrowers are disregarding or disrespecting for the sake of ‘cool’. Finally, does the act of borrowing reinforce stereotypes?
To answer your question, No. Cosplaying in the past hasn’t been used to marginalize, dehumanize, or stereotype the Japanese people. Cosplay has no major religious, political, or spiritual significance, even in Japan it is considered a commercial hobby. Cultural Appropriation is problematic because the hegemonic group (in the US case, white people) get praise for behaviors the group that they borrowed the practice from get penalized for (in this case, Japanese otaku). However, Japanese otaku have the same or superior status as American Cosplayers at US Conventions and English language internet. Japanese Otaku are not facing a double standard when compared to white otaku that favors White otaku.
There are some racists who may say white cosplayers look more like the anime/video game characters then Japanese cosplayer, but those types tend to be seen as racists and pariahs in most well-balanced cosplay communities. Most people tend to think the Japanese have very high quality cosplay.
I enjoy comics too, mainly Judge Dredd, actually nothing else to think about it. I’ve got T-shirts, computer games, loads of comics / books, an Oyster card wallet, badge and cufflinks of JD. You could say I’m a fan. At comic conventions I take interest in seeing the various folks in costume. It’s not my thing, but I get their enthusiasm.
One of the team on my current client in Holland is a huge Star Trek fan. He has all the films and all the episodes. At the moment he’s collecting a part work of all the space vehicles. He goes to events but hates seeing anyone who dresses up and is out of character. “No one from Star Fleet smokes, carries a beer or spends their time on an iPhone”. He doesn’t do cosplay but appreciates those who take the time to add something to the atmosphere of an event by doing it well.
Watching my shy 8 year old and his 10 year brother with the Star Wars guys at a convention made my day. These people enjoy spreading joy. To me, that act of generosity is a big appeal.
No, it is perfectly normal to buy a cosplay costume. Even professional cosplayers buy or get the costume made from someone else. However, making your own costume has a different thrill to it.
What is important though, is how you carry the costume and how much fun you’re having while cosplaying.
As for “devaluing someone’s participation” goes, some may feel that your cosplay is superior to them, when they took more efforts. However, it is not supposed to be that way as these things are done for fun.