Bug 5920 was intended to remove HTML from csv-files Unfortunately that bug overachieved and removed HTML also from tab delimited files - so now there is no easy way to produce HTML-output from Kohas reports
I believe you could use the new feature that links notices as templates to reports, but it would require some changes.
You suggest a different behavior between CSV and Tab export? From a librarian point of view it seems strange. We would prefer more flexibility and clarity, for example a syspref allowing the library to choose whether or not to offer a "csv/tsv with html content" report, which would make the 2 new options available in the drop-down menu
Even better would be four options: csv-without-HTML tab-without-html csv-with-html tab-with-html The new feature that links a report with a template is wonderful, but not a replacement for the lost functionaly - cause someteimes we just want to download the raw HTML and copy-paste into an CMS