Posted in the Technical forum some further findings:
1. Thanks to a suggestion by Dee over in that Thanks Techies! thread, I found that switching to the "NextGen" skin (lower left hand corner, just under "forum jump") resolves my random character and double-spacing issues. However ALL text is now bolded.
2. At least in this particular interface, "Quick Reply" is missing a place to type your quick reply so results in a message that my post needs to be at least one character.
Thought you'd be interested - at least fini.