Yeah, even if it's a short post it doesn't necessarily mean it's spam. A concise reply is actually appreciated a lot of the time. It's a skill that I struggle with, but being concise especially in technical discussions actually prevents confusion. 17 seconds is definitely plausible. There's also the instances where a user might've already written their replies for multiple threads, without being logged in, backed it up, and just copying that over when they are logged in. I've done that sometimes when I'm browsing on the phone, while not being logged in.

I wouldn't say it's normal to be hitting that time limit often, but I can see certain times where a user might run into it.