documentclass[varwidth]{standalone}
usepackage{tikz}
begin{document}
this is line 1\
begin{tikzpicture}path node[draw,inner sep=5mm]{this is node text};end{tikzpicture}\
% MORE SPACE THAN BETWEEN NODE AND LINE 1 (EVEN IF COMMENT IS REMOVED AND LINE IS DELETED)
this is line 2
end{document}

documentclass[varwidth]{standalone}
usepackage{tikz}
begin{document}
this is line 1\

% MORE SPACE THAN BETWEEN NODE AND LINE 2 (EVEN IF COMMENT IS REMOVED)
begin{tikzpicture}path node[draw,inner sep=5mm]{this is node text};end{tikzpicture}\
this is line 2
end{document}