I'm used to the Kate caret which is not a block by default. As I'm seeing in the documentation, it can be changed in Geany to look as a vertical line, but it's not working.
Strange that the cursor is a block, by default its a vertical bar, you havn't said what system you have and where you got Geany from or its version, which may say why its a block. [Ok, you added it while I was typing, know nothing about the Arch package, its not something this project makes]
When you made your `filetypes.common` did you include the section name above the `caret=` setting?