Andrea Federico Grisotto wrote:
For examples looking at this link:
there is a blue vertical line where is quoted plain text,
I have this beautiful behaviour only sometimes in presence of quoted text.
That behaviour presupposes that respective line starts with '>' or '>>'
etc. with *no spaces before or between them*.
How can I obtain nested line with different color in presence of
different level of quoted text?
By avoiding spaces. Spaces between '>' characters are not permitted
according to the applicable standard, and - unlike some MUAs - MHonArc
is standards compliant in this respect.