Saw discussion about “No tags” being the equivalent of an ersatz private post on Tumblr. Here’s what I know: “No tags” equaling “don’t reblog” is a convention that grew in response to Tumblr tag trolls.
There are Tumblr griefers who search on tags like “personal”, “selfie”, “please don’t reblog”, and so on, dedicated to reblogging selfies and other personal content with bullying tags. I first heard of the “no tags means don’t reblog” convention around 2012, in posts about evading Tumblr tag griefers.
But since Tumblr tags have two functions (to organize content within a blog, as well as serving as search keywords for Tumblr at large), Tumblr users who wish to avoid reblogs, but still want to organize their blog for themselves, are in a bind. I know of three methods to get around it: 1. Using nonsensical tags which make sense only to the blogger. 2. Adding unusual prefixes or suffixes to the tags. 3. Starting with five filler tags (Tumblr only indexes the first five tags) followed by the “real” tags.
Ultimately, “no tags” is a response to Tumblr’s lack of privacy tools. If people could make posts that could not be reblogged, or could make follower-locked/non-rebloggable posts, then the “no tags” workaround would be unnecessary. In the absence of genuine functionality, Tumblr users have resorted to “word-of-blog” customs. For instance, some artists post works-in-progress with the tag “wip” for “work in progress” and then get angry if it is reblogged because people “should know” it’s wrong to reblog works in progress.
Since Tumblr’s privacy options are shitty, my response to any “you should not have commented on or reblogged my post for X reason” is to delete my reblog immediately UNLESS the original poster wrote something seriously harmful (racist, sexist, transphobic, etc.) and there is ass-covering going on.
Example: I posted a photo of Benedict Cumberbatch in “12 Years A Slave” and put a blurb under it that said something like “Looking forward to Steve McQueen and Benedict Cumberbatch blowing the ‘good master’ myth out of the water.” Someone reblogged it, removed my comment, and substituted something like, “Look at Benny being nice to his slaves, he’s so handsome.” That seriously happened. I was mad as hell, reblogged their altered reblog, put my original comment back, and ranted. Later the reblogger asked me to delete my reblog of their bullshit. I did not delete it.
However, when the post topic is fandom meta or something equally non-urgent (James McAvoy’s shaved head: hot or not?), then I follow the “don’t reblog” request regardless of the reasons given (or not given, as the case may be; it isn’t really my business why someone does not want something reblogged).
A warning about Tumblr and search engines: choosing the “do not make my Tumblr blog searchable” doesn’t actually work. While the original post will not get indexed by Google, every reblog of the post will be indexed and will turn up in search results if the rebloggers do not also have “don’t make my Tumblr searchable” selected, and many of course will not, since “yes make my blog searchable” is the default. Whether there are tags or not does not matter; the search engines index the post’s content. Since Tumblr can’t make ad money on private and non-indexed content, and making money is the reason for Tumblr’s existence, Tumblr will continue to provide shitty privacy options. It’s this last fact that I think is the most important, and why I comply with “do not reblog” requests.