As Gale wrote, the changed behaviour is almost certainly due to the updated version of WxWidgets.
Regarding the text in the Nyquist message box, automatic text wrap is handled by WxWidgets trying to emulate standard behaviour for the platform that it is running on. Assuming that you have been using the same computer with the same OS X for all of these tests, it would appear that WxWidgets have tweaked the text wrap so that it now occurs at a slightly shorter line length.
For built-in effects we can specify the window size and the text will then automatically wrap to fit the window, but in this case it is a Nyquist plug-in and Audacity does not know how much text will be returned by the plug-in code until the code is returned. The “catch 22” is that Audacity must create the text window first, and then write the text into it, so the window is one that automatically resizes to fit the contents.
An alternative approach that we could take is to make a “standard size” window based on the screen size (say half the height and width of the screen), and provide resizing handles so that the user can resize the window as necessary. This would be much better in cases where the plug-in returns a lot of text, but in cases where a short error message is returned it would look very silly.
A better solution would be for Nyquist to have greater control over how the text box was created, for example, the ability to specify a minimum height and width. This requires further development of the programming interface between Nyquist and Audacity and is something that I am very keen to happen. In Audacity 2.1.2 there has been some development of this. Specifically, Nyquist can now override the default “split line” behaviour when returning audio, two new “numeric text” controls, access to the system time and date, and access to the decimal separator character. There are many other features that I’d like to see, but there are many competing priorities for developer time, and a limited number of developers.
Regarding the “disappearing” meter.
Not only have we updated to a more recent version of WxWidgets, but Mac OS X has deprecated the old “Carbon” API, so there has been a lot of under-the-hood work updating from Carbon to Cocoa. I don’t know whether the change in behaviour is due to the change in WxWidgets or the change from Carbon to Cocoa, but either way I don’t think there will be much we can do about it. We’ve stayed with the old versions of WxWidgets and the old Carbon API as long as possible, but we have to update before they become obsolete and stop working.
The disappearance of “child windows” does not only affect the meters. It affects all floating toolbars, and the “Screenshot Tools” and probably other parts too. Whether the window disappears or not seems to depend on whether it is a “top level” window or whether it is a “child window” (derived from another window). If it is a child window (as in the case of floating toolbars), then when the parent window loses focus, OS X hides the “clutter” because it assumes that you are no longer using them.
To work around the problem, resize the main window a little larger and dock the meter into the main window.