Yeah, this is a problem. People actually do post comments on those threads asking for their username to be changed, even though the change period is over; you just don't see them because we reject them.
I have a big list of threads to write that I hope will form a starters' guide for this community. (You can see the beginnings of that here.) 'How do I change my username?' is one of many threads I plan to create and add to that list. Some others, besides the ones that are already there, include:
- 'How do I ask a good question?'
- 'How do I write a good answer?'
- 'What does it mean when posts are hidden, closed, rejected, etc.?'
- 'I can't find my post. Where did it go?'
- 'My post says it will be checked and approved. What does that mean?'
- 'May I answer my own question?'
- 'What are experts, editors, etc.? How can I be promoted?'
- 'How do I make a good RMT thread?'
- 'When and how should I use sources/references?'
- 'Is it OK to post on old questions?'
- 'How do I know if my question is a duplicate?'
- guides to features like My Updates, favourites, etc.
- links to the Showdown server, Discord server, etc.
Feel free to suggest some others. Most of these are written already, so you should expect a bunch of them to be posted fairly soon. We'd need Pokemaster to change the link in the sidebar when the username change thread is actually posted, though!