Since DW and all plugins have been updated to current versions, I've found that the Comment Syntax Plugin interferes with standard DW syntax.
I have a text where I wanted to quote a whole paragraph in italics, like
//Some text in italics.
Should be just one paragraph.//
This should be normal text.
This worked fine before, as I expected, i.e. the whole text between the leading and ending '//' was displayed using italic font.
However, since the update to Greebo the first line after // is treated as comment, obviously until the end of the line, which matches the docs of the plugin.
Hence, the second line is displayed as normal text, and due to the '//' at the end of the second line all subsequent text is displayed with italic font.
The fix is to enclose each line of the 'italics' paragraph in '//' pairs, as in
//Some text in italics.//
//Should be just one paragraph.//
This should be normal text.
In the DW forum I got an advice to open a bug here:
https://forum.dokuwiki.org/thread/15965
However, I'm not sure what should be the expected behavior. From the plugin's point of view the new behavior sounds reasonable, but if it is then maybe there should be a note in the plugin's docs that this may interfere with the notation for italics font.