Unless it is otherwise clear from the subject of the title, I like having some obvious indication which aspect of the site you're talking about.
Consider the original title:
Unable to follow links in comments
When I first read that, I assumed it was on the main site and was very confused. Since there are comments both on the web site and in the Android app, it is impossible to differentiate which you are talking about from the title itself. What you're asking about becomes much clearer if you add that you're talking specifically about the Android app.
Yes, it is already in the tags. That serves a different purpose: one related to categorization, not description.
And of course, not all of the information in the tags needs to be added to the title—just pivotal things. Remember that the purpose of a title is to summarize the question/problem. Clarity is paramount. That you are unable to follow links in comments is not an adequate summary of the problem, because that statement is not generally true. It is only true under certain conditions, when you're using the Android app. That information rightfully belongs in the title. I mean, it's not like the title was already so long that adding "on Android app" pushed it over the edge.
It's no different than if you had posted the following question:
Unable to post anything to the site
and then, upon reading the question, I found out you were talking only about chat. That title would then be misleading and in need of an edit. Because at first blush, it would look like you couldn't post anything anywhere, which is clearly not true: in this hypothetical scenario, you had no problems posting questions or answers.
This is just a specific example of the more general rule that it is perfectly fine to include information from the tags in the title as long as you integrate it organically. The title
Android app: Unable to follow links in comments
would be horrible.
It is also unnecessary to integrate the "bug" tag into the title in any way whatsoever, because it is already obvious from the title's summary of the problem that you're reporting a bug. You would not say either:
Bug: Unable to follow links in comments on Android app
Bug where I am unable to follow links in comments
This argument that none of the information that appears in the tags needs to be included in the title is absurd. If that were true, we wouldn't even need titles. Tags would be sufficient. If a question is well-tagged, a title could be virtually assumed. Yet no one would seriously propose eliminating question titles.
Then again, I can't say I would want to require that all Android questions have this added to their titles. Nor would I edit all questions to make this change. I only added that while I was making other improvements, namely resizing the image to something that didn't take up my entire monitor.