I know the default position of the Read More or '[...]' tag is under the excerpt, but is it possible to add the '[...]' directly after the excerpt that is cut off, thus indicating that the text actually continues? When looking at an excerpts page (e.g. category page) that is not directly obvious (to me, at least). Or, is it possible to add just some trailing dots, e.g. '...' where the text is cut off?

There is no line break by default, and you can edit the ellipsis [...] to anything else at Configure EXCERPTS -> Custom Read More, in the newest version 3.4.2

You're right. Totally my fault. I was using the <p>Read More...</p> example supplied in the options without even considering using the default '[...]'. Somethimes I tend to click before I think (no pun intended).