Implies arrow looks off

Question

So I've compiled my latex code and I found that the implies arrow looks slightly distorted

Is this normal, and is it possible for me to fix this?

EDIT: a snippet of my code below:

\documentclass[15pt]{article}

% define paper margins
\usepackage[
    a4paper,
    portrait,
    top=1.2cm,
    bottom=1.2cm,
    left=1.5cm,
    right=1.5cm,
    headheight=15pt, % avoid warning by fancyhdr
    includehead,includefoot,
    heightrounded % to avoid underfull messages
]{geometry} 

% Make justifications better.
\usepackage{microtype}

% Allows inclusion of sample text.
\usepackage{blindtext}

% Gets outlines right.
\usepackage{bookmark}

% ams stuff
\usepackage{amsmath, amsthm, amssymb}

% Bold math for vectors and the lot.
\usepackage{bm}

% Allows inclusion of special spaces
\usepackage{xspace}

% fancy headers
\usepackage{fancyhdr}
\pagestyle{fancy}

% Allows inclusion of custom fonts.
\usepackage{fontspec}

% Allows the use of custom enumerators in lists.
\usepackage{enumitem}

% Allows drawing of graphical images.
\usepackage{tikz}

% Allows inclusion of images.
\usepackage{graphicx}

% Allows inclusion of links
\usepackage{hyperref}

% Allows boxes to be drawn around text and math environments.
\usepackage{tcolorbox}

% Includes extra mathtools.
\usepackage{mathtools}

% hyperref setup
\hypersetup {
    colorlinks=true,
    linkcolor=blue,
    filecolor=magenta,
    urlcolor=cyan
}

% Paragraph indenting and skipping.
\setlength{\parindent}{0cm}
\setlength{\parskip}{1em}

% Augmented Matrix environment.
\newenvironment{amatrix}[1]{%
  [\begin{array}{@{}*{#1}{c}|c@{}}
}{%
  \end{array}]
}

% Commands
\newcommand{\latex}{\LaTeX\xspace}

\renewcommand\qedsymbol{$\blacksquare$}
\newcommand{\reals}{\mathbb{R}}
\newcommand{\naturals}{\mathbb{N}}
\newcommand{\integers}{\mathbb{Z}}
\newcommand{\rationals}{\mathbb{Q}}
\newtheorem{theorem}{Theorem}
\newtheorem{lemma}[theorem]{Lemma}

% Fixing brackets
\let\originalleft\left
\let\originalright\right
\renewcommand{\left}{\mathopen{}\mathclose\bgroup\originalleft}
\renewcommand{\right}{\aftergroup\egroup\originalright}

\DeclareMathOperator{\Tr}{Tr}
\DeclareMathOperator{\sgn}{sgn}
\DeclareMathOperator{\lcm}{lcm}
\DeclareMathOperator{\Span}{Span}

\DeclarePairedDelimiter\ceil{\lceil}{\rceil}
\DeclarePairedDelimiter\floor{\lfloor}{\rfloor}


% Font
\defaultfontfeatures{Mapping=tex-text,Scale=MatchLowercase}
\setmainfont{Roboto}

% Title
\title{test document}
\date{\today}

\begin{document}
\begin{align*}
    \frac{c-b}{2} &= \prod_{q\in Q}q^2 & \frac{c+b}{2} &= \prod_{s\in S}s^2\\[1em]
    &= \left(\prod_{q\in Q}q\right)^2 & &= \left(\prod_{s\in S}s\right)^2\\[1em]
    &\implies \text{blah blah blah}
\end{align*}
\end{document}

Answer 1

There’s one set of answers here. However, this is one of those pieces of decades-old technical debt that you can sweep away by using the modern toolchain.

Specifically, if you use the unicode-math package, and compile with LuaLaTeX, it will use the Unicode symbol for ⇒. (I would recommend LuaLaTeX over XeLaTeX because it supports the font expansion feature of microtype.)

\documentclass[15pt]{article}

% define paper margins
\usepackage[
    a4paper,
    portrait,
    top=1.2cm,
    bottom=1.2cm,
    left=1.5cm,
    right=1.5cm,
    headheight=15pt, % avoid warning by fancyhdr
    includehead,includefoot,
    heightrounded % to avoid underfull messages
]{geometry} 

% Make justifications better.
\usepackage{microtype}

% Allows inclusion of sample text.
\usepackage{blindtext}

% Gets outlines right.
\usepackage{bookmark}

% ams stuff
\usepackage{amsthm}

% Allows inclusion of special spaces
\usepackage{xspace}

% fancy headers
\usepackage{fancyhdr}
\pagestyle{fancy}

% Allows the use of custom enumerators in lists.
\usepackage{enumitem}

% Allows drawing of graphical images.
\usepackage{tikz}

% Allows inclusion of images.
\usepackage{graphicx}

% Allows inclusion of links
\usepackage{hyperref}

% Allows boxes to be drawn around text and math environments.
\usepackage{tcolorbox}

% Includes extra mathtools.
\usepackage{mathtools}

% Use Unicode math fonts.
\usepackage{unicode-math}

% hyperref setup
\hypersetup {
    colorlinks=true,
    linkcolor=blue,
    filecolor=magenta,
    urlcolor=cyan
}

% Paragraph indenting and skipping.
\setlength{\parindent}{0cm}
\setlength{\parskip}{1em}

% Augmented Matrix environment.
\newenvironment{amatrix}[1]{%
  [\begin{array}{@{}*{#1}{c}|c@{}}
}{%
  \end{array}]
}

% Commands
\newcommand{\latex}{\LaTeX\xspace}

\renewcommand\qedsymbol{$\blacksquare$}
\newcommand{\reals}{\mathbb{R}}
\newcommand{\naturals}{\mathbb{N}}
\newcommand{\integers}{\mathbb{Z}}
\newcommand{\rationals}{\mathbb{Q}}
\newtheorem{theorem}{Theorem}
\newtheorem{lemma}[theorem]{Lemma}

% Fixing brackets
\let\originalleft\left
\let\originalright\right
\renewcommand{\left}{\mathopen{}\mathclose\bgroup\originalleft}
\renewcommand{\right}{\aftergroup\egroup\originalright}

\DeclareMathOperator{\Tr}{Tr}
\DeclareMathOperator{\sgn}{sgn}
\DeclareMathOperator{\lcm}{lcm}
\DeclareMathOperator{\Span}{Span}

\DeclarePairedDelimiter\ceil{\lceil}{\rceil}
\DeclarePairedDelimiter\floor{\lfloor}{\rfloor}


% Font
\defaultfontfeatures{Scale=MatchLowercase}
\setmainfont{Roboto}[Scale=1.0]
\setmathfont{Fira Math}

% Title
\title{test document}
\date{\today}

\begin{document}
\begin{align*}
    \frac{c-b}{2} &= \prod_{q\in Q}q^2 & \frac{c+b}{2} &= \prod_{s\in S}s^2\\[1em]
    &= \left(\prod_{q\in Q}q\right)^2 & &= \left(\prod_{s\in S}s\right)^2\\[1em]
    &\implies \text{blah blah blah}
\end{align*}
\end{document}

I chose Fira Math as the math font above. As of 2020, it’s the only sans-serif OpenType math font.

That sample is nearly identical to your MWE, minus a few packages that are obsolete when using unicode-math (bm, amssymb) or already loaded by it (amsmath, fontspec). I also removed the redundant Mapping= option from fontspec.

There is one change you would need to make to your source: if you had been using \bm, you would use \mathbf instead. (Or \mathbfup for upright, \mathbfit for italic.) You say in the comments that you want this for vectors. If that’s all you need, you can stop reading here.

The \boldsymbol command still works, as does \boldmath and \mathversion{bold}. These are the only way to get bold operators. However, as of 2020, the only free math fonts that include a bold version are XITS Math and Libertinus Math. If you load one of those, it will automatically enable \boldsymbol, but otherwise, you need to add a command such as

\setmathfont[version=bold]{Libertinus Math Bold}

In a pinch, you might even try,

\setmathfont[version=bold, FakeBold=1.2]{Fira Math}

But I don’t recommend it.