For me, such tags are enabled by default. You can configure which task tags should be used in the workspace options: Java > Compiler > Task tags
Check if they are enabled in this location, and that should be enough to have them appear in the Task list (or the Markers view).
Extra note: reinstalling Eclipse won't change anything most of the time if you work on the same workspace. Most settings used by Eclipse are stored in the .metadata folder, in your workspace folder.