Suggestion: when you're building a user database, assign each user a 16-digit hexadecimal number as a unique identifier, disallow that internal identifier from changing, and let everything else change.
Want to change your username? Great. Want to change your email? Fine. The unique hex ID is all that matters.
16 hex digits is enough collision space to give every person on earth about 2.5 /million/ accounts on your system, but short enough that you can write it down on a post-it note.
If you're going to add a disingenuous "Thanks" to your email signature, maybe leave a post-it so that you don't end up replying "Thank you"
You'll notice that companies advertising clothing and accessories on Instagram don't put prices in the ads, because they're all overpriced for what you get. $75 hoodies? $200 winter boots? $3700 watch that's indistinguishable from a $200 one? $2000 leather briefcase that's also a backpack? Plain T-shirts for $60 each? it's like they think people haven't heard of eBay and Amazon and can't get good versions of these for 5%-50% of those prices.
Wow Discord's UI is terribly designed. Why have a notification count at the top that you can click if it just takes you to your friend's list with no notice of what that count is.
For the record it was suggested friends, which was 3 clicks from the friend's view to see. It's still a horrible design.
Hopefully this turns out better.