It's pretty simple actually: First, when you type @a, scratch recognizes this as a user ping, and will automatically add a hyperlink and a space in between it and the next thing typed. This means that if you type @a@a like this, scratch will separate it out in the comment as @a @a. However, when scratch adds that space, it doesn't check to see if the new spaced out @'s are taking up more than 500 characters, thus, it turns out to about 700-1000. Hyperlinks generally take up a little bit more ram than regular text, and if done 500 times over, will severely damage the performance of the page. When I tested this on my profile, it lagged a lot. Spamming @a enough and quickly enough can cause the page to be so slow that it crashes.
I AM NOT RESPONSIBLE FOR ANYONE MISTREATING THIS INFORMATION.
