Now that you mention it, I've seen this before when I was reading tons of RACE games, though I thought nothing of it.
And look at that! My QA experience comes in handy!
Based on the examples you've provided, I've found the cause (though I don't understand why it does what it does):
This happens when the last "In play" thing (unit, building, whatever) has been given not just parenthetical stats, but a further square-bracketed ability note.
I think somehow the closed square bracket, or maybe the whole bracketed word/phrase is causing the problem. Maybe the forum tries to read the bracketed piece as a tag? And since it doesn't recognize it, it just prints it as text? But trying to read it as a tag somehow messes with the following line break?
Looking back at my games, I don't see it in any of my posts, but I'm quirky, so I put all notes in parentheses next to the stats (never using square brackets).
Poking @zhavier in case he would otherwise miss this post.