I notice that the first text line below the Title line in each index card is shorter in line height than the rest. Is this intentional? The Synopsis is the reverse; there, the first text line below the Title line has more line height available than the other lines.
This is probably best described with a screenshot, as it might depend on many user options.
The second image is not from an Index card but from the Inspector. The synopsis text area have margins around, which make the first line look taller.
I know but still, I think this is what @rwfranz meant by pointing out the Synopsis. If you exclude the Outline View and those two places are there any other places where the synopsis is displayed?
Heh. Okay. The normal line height varies with the font selected for the cards, but the change in height seems to be consistent.
Right now, i have the cards at 4x6". The size of the card does not change the 1st line’s height relative to the other lines. The font used does not either. The first line of TEXT (not the Title) seems to be about 75% of the rest of the lines. That is, where the text says “Just you and your words with no distractions”.
Note, the font does not change. It just has less headroom.
On the first card (Main Interface), there’s an “f” in “interface” with a few pixels of headroom, in the first line. In the third line, there’s an “f” in “file” (and also in “following”) with nearly twice as much headroom. This can also be seen in the “ll”'s in “all” in the third line, and “following” in the first line.
The first line (using 12-point font, I believe) is 18 pixels high (measured with Gimp crop tool, zoomed in) bottom of the line above to the bottom of the line the text stands on. The second line is 23 pixels high.
If I shift the font to 20 pts, the first line is 30 pixels high; the 2nd line is 38 pixels high.
If I shift to 48 pts, the first line is 69 pixels high; the 2nd is 88 pixels high.
Here’s a partial screenshot of the 48-pixel version.
Hope that’s enough. As demonstrated in Krastev’s post, the Synopsis in the Inspector does not have this issue; the 1st line has more headroom than the rest of the text lines. In the index cards, the first line has about 1/4 less height. Is this intentional? That is, does the Mac version do this, too?
The synopsis text has a top/bottom/left/right margin. Because of this the first line will always be taller. The line spacing depends on the font being used. The line spacing is always 1x. Mac also has margins. Scrivener for Win is ready for release, if we start discussing similar issues. 
Hate to argue here, but the first line is NEVER the same as the rest of the lines in the index cards, no matter what font I use. The Title line has its own font; not talking about that line, either. But the first line of the text on the card (excluding the title line) seems to have a line spacing of about 0.76x.
(and I agree it’s a minor thing. I just wonder why that is)