Spacing between normal text and other text increases unwanted and too much, please see the example below made with version 1.2018.10
@startuml
start
:asdf asdf asdf asdf :asdf asdf asdf asdf asdf asdf asdf asdf asdf __ASDF ASDF__;
:asdf asdf asdf asdf :asdf asdf asdf asdf asdf asdf asdf asdf asdf **ASDF ASDF**;
:asdf asdf asdf asdf :asdf asdf asdf asdf asdf asdf asdf asdf asdf ""ASDF ASDF"";
:asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf ""ASDF ASDF"";
:asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf ""ASDF ASDF"";
:asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf ""ASDF ASDF"";
:asdf asdf asdf asdf asdf asdf asdf asdf asdf ""ASDF ASDF"";
:asdf asdf asdf asdf asdf asdf asdf asdf ""ASDF ASDF"";
:asdf asdf asdf asdf asdf asdf asdf ""ASDF ASDF"";
:asdf asdf asdf asdf asdf asdf ""ASDF ASDF"";
:asdf asdf asdf asdf asdf ""ASDF ASDF"";
:asdf asdf asdf asdf ""ASDF ASDF"";
:asdf asdf asdf ""ASDF ASDF"";
:asdf asdf ""ASDF ASDF"";
:asdf ""ASDF ASDF"";
stop
@enduml