The link in the discussion thread looks like a link and does not work. Either it should NOT look like a link, or it should work.
You can find the example in this course (https://courses.edx.org/courses/course-v1:UTAx+CSE1309x+2016T1/), search for thread "doubt" (should be linked here: https://courses.edx.org/courses/course-v1:UTAx+CSE1309x+2016T1/discussion/forum/5560b90cc9eab5e5f63980d3d1a66c0f990d3567/threads/574ec751e1362905500005ed). The first response, from bribre, has a link to the "thread" in the response body.
All HTML links i.e. <a> tag elements should be clickable.
Plain URLs should also be clickable.
Other than that phone numbers, emails and map links should also open respective app on the device e.g. tapping a phone number should open the Phone app.