In the Scripts Editor I noticed that the scrollbar can't possibly go 100% down, instead always leaving a small space.

Confirmed in 7.25.

Unless you're seeing something different, the tiny space is there also when scrolled to the top and can also be seen in any window in mIRC. I also just tested in Firefox and saw the same tiny space. It looks like it's just a Windows scrollbar display thing rather than something in mIRC. It's the same in mIRC 6.35.

If you're seeing something different than that 1mm (probably more like .5mm) space between the bottom of the scrollbar and the top of the down arrow on the scrollbar, then please post a screenshot because I'm not seeing that.

Could you clarify what you're talking about? I don't see this bug in other windows inside mirc, nor have ever seen one in firefox or chrome. I usually see these bugs in poorly written small applications. That's why I'm surprised about this happening in mirc.

I hope I don't need to post a picture about this, it's very easy to reproduce.

Maybe it's easy for you to reproduce but I see no differences between mIRC's scrollbar and any other program.

He's not talking about that tiny space that you mentioned.
mIRC adds a new line in the end of the script editor, but it just doesn't let you to scroll to the end of editor. However, you can scroll to the very bottom using Arrow Keys.
I guess that's what he's talking about.

For me on Win7, there is no way it could be 100% down after you touch it. If you don't touch it, this doesn't apply. And there is zero logical explanation of why this would be a useful behaviour. I see it as a programmer's error which can be easily corrected within a few seconds. And this is in 7.25

Here is the picture:

Confirmed on mIRC 7.25 and Win7 x64

It's been like this for as long as I can remember using mIRC.

Ok, after further testing, I see it now. It has to be a small script to be noticeable. Most my scripts are hundreds of lines or longer, and at that size, no noticeable difference is there between this app and any other app which is why I couldn't see it originally. However, when under 150 lines or so, it can be seen. So this only appears when looking at short scripts and the amount of space is dependent on the number of lines as smaller scripts have a larger gap than larger scripts -- compare a 50 line script with a 150 line script, for example.

And just for more information, a small script on 6.35 also exhibits this behavior when I tested that. And once again, the larger the script, the smaller the space until around 150 or so lines, it becomes unnoticeable. So it's been that way since at least 6.35 and isn't a recent change in case that's helpful for Khaled.

I think you're being distracted by the symptom and not looking at the cause. The bug[*] is simple: it's impossible to scroll to the last line of text in the editor using the scroll bar, mouse wheel, or down arrow if the last line is blank (which, it usually is, since mIRC automatically puts a newline after the last non-blank line). Although you can get to it by using right arrow at the end of the last non-blank line.

[*] I think this might be intentional behavior.

This appears to be a richedit control issue. If there is a blank line at bottom of the text, it does not allow you to scroll down to it unless you use the arrow keys. As the editbox scrollbar and display are managed by the richedit control, there is no way to prevent that.

The reason there is a blank line at the end of the text is that lines are separated by CRLFs. So one solution might be to remove the CRLF from the last line to prevent a blank line appearing at the end. However that means in order to add new text to the end, users would have to scroll to the last line and press return. I prefer having a blank line at the end, so I would rather leave it as it is.