Understandable... may i suggest do your normal long password and just start with a capitol letter and end with an exclamation point. If you're doing your normal long secure password it should still work nicely. Or are you saying keychain doens't allow for over 8 characters?
It's also my understanding that you're just preventing someone who has physical access to your computer right?
This is exactly why it doesn't make it more secure. Everyone just starts with a capital and ends with a number and an exclaimation point or replaces i's with 1's, etc.
My point is that it doesn't make it more secure. In fact, it makes it less secure, and harder to remember. It means that when they do a dictionary attack, they can eliminate all entries without a capital or number or special character, testing less passwords.
You're preventing anyone that gets hold of your keychain password file or physical access. So, if you get hacked, or your computer stolen, or if you live with someone that's a dick.
Currently, not a ton of people use Steem, so the chances of your accounts getting compromised before you can change the passwords isn't huge. So the main problem is that it's annoying and has no useful purpose.