No, I swear black and blue.
An application or a website should remove all following space characters from a string.
If it does not, you may get a problem which makes you crazy even annoyed.
Many years ago there was a similar problem in Microsoft Access when saving a record with a field containing following space characters. Microsoft reacted and newer versions of this product cut the contents and strips off all following space characters the user entered in a field.
About what are we talking?
The E-Mail address was entered as a shortcut in
Settings – General – Keyboard – Shortcuts
with the phrase email@example.com and the shortcut aid.
If you use the shortcut iOS appends a blank, 1Password saves it and Apple’s website informs you about wrong credentials.
Using shortcuts on Apple’s devices is a frequently used and highly comfortable feature.
And adding a blank after using a shortcut is a sensible behavior of the operating system.
So Apple certainly cannot bear the blame.
This problem with following blanks does not occur in all cases. Some apps or websites ignore following blanks as anybody would expect. What should a blank character be for? Nobody can see it.
From a more technical point of view a string with a following blank and a string without are different contents when saved to memory. From the users point of view it makes definitely no sense to handle usernames in such a way.