What browser and version number this was seen on Safri (iPhone) iOS 12
The operating system iOS 12.2
A description of what is happening compared to what should be happening The post editor on small viewport devices is not the rich text editor as used on larger screens. It is some form of smart text editor. Experience suggests that on posting from that editor, text is parsed and special characters (ampersand, greater-than, less-than, non-breaking-space etc) are converted into their HTML special character form as in...
All is fine until one attempts to edit in the small viewport editor a post created in the small viewport editor...
HTML is (to varying degrees of sensibility) stripped out, except the encoded HTML special characters which then just appear in the text as text, viz...
Double spaced text
Becomes
Double spaced text
Which upon being saved, is not saved as HTML special characters, but as literal text.
Whatever the smart small viewport editor can encode into HTML it should be capable of decoding, so if it converts "double space" to "a space and a HTML non-breaking-space" then that is what should be seen on seeking to edit the post.
The steps needed to replicate the problem
Create post on a smart phone which does not use the rich text editor, which has characters which will be encoded as HTML special characters (double-space is a favourite!)
Save the post
View the new post and select edit post
Observe the rendering of HTML special character codes as plain text
Save the post, observe that the HTML special code characters now form part of the post's text
The URL where the problem occurs Any post created and edited on the small viewport editor