"Can I set a custom font? Right click to save a linked image? Drag a block of selected text to save it, or from elsewhere into a text box?"
Yes, as long as it's in a format recognized by your system and does not contain unrecognized (i.e unstandardized) character information
Yes, you can if people bothered implementing two lines of code to enable that in the right-click context menu
Yes, but sadly it hasn't been implemented prior to Flash Player 9+, which is now standard.
I do agree; Flash for /plain text/ is pointless. You use HTML and CSS presentation for that.
But Flash is far from buggy, although it is inaccessible due to it being a plugin. However, accessibility is not always a prime concern. Currently I'm writing a PowerPoint-ish net based software for corporate use, using Flash. What does it matter if it isn't accessible to people who don't have Flash installed? It's still more accessible than an application you have to download, install and let loose upon your local system. Flash has its uses, but can't be used for every thinkable scenario. The same goes for anything that is to run in a browser.