I have a similar problem (I'll see if I can produce a sample file that reproducibly does this). A few things that I've noticed concerning this topic:
In documents with this problem, some (most) documents seem to randomly (?) turn bold on loading the file. This might be related to the font set in the document.
In documents with this problem, the text cursor will always be set to bold, even if the surrounding text is not bold. (This is what the document would look like if the text actually was bold:)
One one of the affected computers, the problem extends to the formatting dialog:
A possible cause I've found is that all affected computers were used to work on a Scrivener file containing the Vollkorn font: normally, in the font style selection dialogue, fonts list "Standard" first, followed by "Bold", "Bold Italic" etc.; the developers of Vollkorn seem to not have taken care of this, hence "Bold" is at the very top of the selection menu. It seems to me that Scrivener has automatically selected the "Bold" style due to it being "on top" and therefore decided to make everything bold -- something that could also happen with other fonts that have the same issue. However, it seems incredibly difficult to tell the program to stop doing this, at least I haven't found a way to consistently do this, even when changing to a different font.
I hope this can at least help pinpoint the problem!
I am having this same issue. I had no problems in Scrivener one, but in the Beta everything is BOLD no matter what I do. I'm using a Baskerville font. Same as I did in Scrivener 1. If I highlight and remove the BOLD it is there again the next time I open the document. It's very frustrating. Is there a fix for this yet?
Sorry guys, this fix did not make it in the Beta 28 release, but will be available in the next update.
Just want to point out that some of the fonts do not provide multiple font weights. For example "TypewriterScribbled" has only a font weight of 57, which is called "Medium", which is neither Normal, nor Bold. Have in mind that the RTF spec does NOT allow specifying font weight explicitly, but only bold/non-bold font style. In this case the font definition provides only one font weight. Scrivener is trying to find the best font weight match for bold/non-bold cases out of only one available font weight for this font, which is obviously asking for troubles.
Most of the fonts given as examples above have similar issues with only limited or non-standard font weights defined. Still Scrivener will handle these cases much more gracefully in the next update.
I filed a similar problem some time ago -that text set in italics (by ctrl+I) returns in the "weight" italics, and still itaicized (so it tilts a lot...). I use Book Antiqua. Don't know if that is related, or whether it has been adressed?