The question is about consistent vertical spacing in a paragraph of text that includes some math using subscripts.
Concretely, in the example I feel that there is not enough vertical space between line 1 and line 2, due to the fact there is both a subscript in the math on line 1 and some math as well on line 2.
In general, I would not want to fix this locally, but rather have a bit more vertical space consistently throughout the paragraph (whenever the situation occurs at least once in the pargraph).
Since I have a quite a lot of paragraphs where this situation occurs, it would be useful if I did not have to request that for every single paragraph, but if this could be a default.
Thanks for reading.
\documentclass[draft,11pt]{article}
\sloppy
\usepackage{amssymb}
\begin{document}
\newcommand{\diam}[1]{\ensuremath{\langle #1 \rangle}}
\newcommand{\model}{\mathbb{M}}
\newcommand{\N}{\ensuremath{\mathsf{N}}}
Assume $\model|_{\N(w_0)\cap\ldots\cap\N(w_n)},w\models \diam{a}\psi$.
It follows that there is a state $v\in \N(w_0)\cap\ldots\cap\N(w_n)$
with $w R_a v$ (1) and $\model|_{\N(w_0)\cap\ldots\cap\N(w_n)},v\models
\psi$ (2). Hence by IH $\model| _{\N(w_0)\cap\ldots\cap\N(w_n)},v\models
\psi$ (3). From (1) and the fact that $\model'$ is an $A$-generated
submodel of $\model$ we have $w R'_a v$, hence by (3) $\model'| _{\N(w_0)
\cap\ldots\cap\N(w_n)},w\models \diam{a}\psi$. The other direction is
trivial.
\end{document}


\linespread, but if you do so, I would advise you to do it (for consistencyś sake) for all your document, in which case, the setspace package will be useful. – Gonzalo Medina Jan 23 '14 at 17:20