As per the stats, it's actually 25% - there were total 149 migrations in the last 3 months and of that 84 were to Web Apps.
25% of 84 ~ 21 rejections over a span of 90 days is think not that big of a number.
I was the one that migrated the question. In retrospect, I probably should have left a comment as to why I made the decision, so for that, I apologize.
You asked two sub-questions, and I will address them separately.
Why was Wunderlist designed to not work in private browsing mode in Firefox?
This first question, asking about the company's reasoning/...
Everything has now been migrated to Superuser. I have voted to close the second question as a duplicate of the first there. All of the answers migrated over.
We could certainly debate the decisions that were made, but there were no actual rules broken here, and as such, no action will be taken beyond what has already happened.
Google Calendar web UI doesn't have anything that could help,
If I would like to research in order to write an anwser to that Q, I would start by looking at Google Developers, actually I would go directly Google Calendar API
So, IMHO, the related Q should be migrated to StackOverflow.
It's actually not that bad - here're some stats;
193 migrations in the last 90 days
superuser.com → webapps.stackexchange.com × 97; 16% rejected
programmers.stackexchange.com → webapps.stackexchange.com × 2
From Meta Stack Exchange:
Starting [December 10, 2016], these should be deleted automatically 30 days after being rejected.
Note that this logic will only delete a rejected, migrated question if it meets the following criteria:
Migrated from another site (and no moderator has cleared the migration history)
Not already deleted
Closed (but not as a duplicate)...
As mentioned in the comment, if a site is not present under the Migrate list, click on Flag → other (needs ♦ moderator attention) and mention to which site it should be migrated to.
We'll migrate if it fits
Five users on Super User decided that it was off topic and at least three of them decided that this site was a better place for the question. I don't know enough about the app to know for sure whether they were correct.
We as a community can decide whether or not we want to keep the question by either leaving it open or voting to close. However, if we vote ...
I suspect anyway, that it is a natural result of this site being opened.
Web Apps was the first site opened via Area 51
Before that, there had been a number of (off-topic) web app related questions on Super User1
Web Apps has been a migration target from Super User from the beginning
What's probably happened is that there was a lot of pent-up ...
3 posts that you submitted suggested edits for were removed. This causes you to lose 6 reputation. 2 reputation for each edit.
When viewing your reputation, if you check the box at the bottom of the page called "show removed posts" it should display these posts and the subsequent reputation loss.
When you flag select the "in need of moderator attention" (or "other") option on the first dialog and explain where you'd like the post to be migrated to.
However, please bear in mind two things.
We don't migrate crap. So if the question is not a good question don't flag it for migration. Just vote/flag for it to be closed and perhaps leave a comment ...
A large number of the Android questions we get are simply because Google figures significantly in Web apps. People don't realize that Gmail questions (for example) may not belong here. We get many fewer questions that should go to Ask Different.
I say it would be worthwhile to add it now. We can always revisit in the future.
I think migration to Android/WP/Apple site is a rare exception(per stats, questions getting migrated to Android is about a third of what gets migrated to Stack Overflow and a tenth of what gets migrated to Super User).
I don't think we need to place one in right now..
The question wasn't about usage of a webapp. Should it have been migrated to Super User? I'd think not. (Note: I'm a Super User Moderator too.)
This line from OP:
How can I get out these textareas using keyboard so I can continue switching fields?
Made me assume he's working on a webpage he's working on webpage and needs suitable method to implement ...
I would migrate only questions that have the google-spreadsheet tag or can be edited to have the google-spreadsheet tag.
Questions, in combination with the google-apps-script tag are a little bit tricky. The Google Apps Script Developers chose Stack Overflow as their primary Q&A site for related questions. Therefore I would leave them.
Not everybody, ...
Use the "other" option when flagging for moderator attention and ask for it to be migrated. However, always bear in mind the first rule of migrations:
Don't migrate crap
So it better be an otherwise excellent question that just happens to be on the wrong site.
However, be aware that there are over 1,500 flags outstanding on Stack Overflow at the moment ...
It's not off topic.
Tumblr is a web application, so a question about how to configure it is very much on topic for us.
Yes you have to write code, but it would probably get closed very quickly on Stack Overflow.