As I do more management (yuck) I find myself having to put together reams of commented screenshots all the time. My process for this is piecemeal - but this would definitely help. Thanks!
A few suggestions:
1. HTML, Google Docs, or PDF output would be faaaar more useful than Word. I'm actually surprised you used Word here. We must have very different work environments. :)
2. I feel like there are usability/UX recommendations other than Nielsen that might be more useful for some audiences. His advice is a bit mundane and abstract for my tastes. Perhaps the https://userium.com/ list could be of use for some. Having options here (which I agree stinks of bloatware) could be interesting.
Oh.. and extra points for using a .CO :)
1. There actually already is HTML output. My idea is that most people will likely copy/paste from HTML or a Word Doc to combine with their collaborators. From that perspective, PDF feels too 'finished'. And yeah, as someone else explained, I'm a PM on the Office Online team :)
2. This is great. I'm working on supporting different lists than just Nielsen's heuristics (including being able to create your own custom list). Unfortunately the one you linked to is quite long and might be quite lengthy to have in the sidebar. I'll think about that though.
I'd love to see a simple, open output format too. The source is up on github: https://github.com/cgallello/UXCheck.
My problem with Invision, which we used extensively about a year ago to redesign POP.co, is that it expects you to live in its own interface and interact with the Invision prototype on their own terms, inside their walled garden of sorts.
This is OK, and kind of makes sense in the app-driven world we live in, but to really fit into the kind of hectic, ten-different-tools workflow that we thrive in at the office, screenshots are the core lingua franca.
We can attach them to Pivotal tasks (or Hipchat convos, or anything else), forward them around (even via SMS!), scribble all over them, print them out and stick em on the wall for a meeting.
With Invision, we'd be crowded around a phone or screen, and unable to interact with the collaborative output in other tools. I came to dread receiving an Invision link in my email, especially because I couldn't tell which shortened URL referred to which project.
Overall, I've come to really hate tools that expect me to live inside them, rather than them living inside everything else I already use. I don't want to leave my flow.
Hope that made sense. :)
There's also a larger lesson to be learned about finding the integration points that make the most sense to the application you're building. Things like email and calendars are obvious, I wonder what else should be considered from the same point of view.
Rather than the sense of dread you mentioned, I just let other things take higher priority than the emails with Invision links. I thought it did work well when a designer led a small group through a prototype live.
If you're considering what TLD to use for your next project, .CO gives you a ton of great freebies with their membership program. Worth a look.
EDIT  whoops forgot the link thanks pc86 http://www.go.co/members/
Even though a lot of the offers are closed (would be nice if I could filter those out) there are still some handy deals in there.
I actually use a .co domain and had no idea about this program, so thanks to the GP!
Things have gotten better now, and millions of people have interacted with t.co, the Twitter shortener, Vine, etc., which means that .CO isn't quite as "underground" as it used to be.
I think ultimately the choice of TLD should be related to other branding decisions in that you consider your market first. So if you are pursuing a group that's very internet savvy, or startup savvy, they've probably heard of .CO and you can use it freely. (Likewise, you could probably use an unusual/industry name)
But if you are going after people who aren't familiar with URLs or domain names -- or maybe can't even discriminate between an email address and a domain name -- you'd be better off going with the safer option.
Your website had me thinking the tool was going to perform an automatic scan for usability issues. You could be a little clearer that the tool allows users to note usability issues.
Speaking of user experience, you should really use inline installation for chrome extensions. It provides a really nice experience so that users don't need to leave your site. It also allows you to detect if the extension is installed so that way you can remove the install button for people who already have it.
Note: The highlight box seems to be slightly misaligned vertically on some sites. On one site I tested it seemed to be ignoring padding-top on the <body>.
Also, what would be really handy is the ability to download the result not as a document, but rather to integrate it with existing issue tracking software such as JIRA. I'm sure that's on your V2 plans with some monthly recurring plan.
If I manually add "font-size: 16px;" to your html,body CSS definition, everything displays properly. The discrepancy is occurring because you are using a fixed pixel height (eg: for the "ten heuristics" div its height is 500px) but letting the browser/system determine the font size.
I've been working on that topic too in the last year. I developed Capian (http://capian.co), a tool to help usability professionals make better heuristic evaluations faster.
I'm a full-stack developer and my partner is a UX designer. There's a lot of missing tools in our space. Great to see other people trying to address them!
When selecting "Other" in the heuristics dropdown allow you to enter your own in a text field.
4 levels of severity seems unnecessarily limiting - 10 would be nice
Just curious, what do you use to create the docx in browser?