This is a discussion that comes up frequently. There is a huge dividing line on this subject,with emotional arguments and no real resolution or definition of when to do the activity. I agree with the article that there are times such as real tight or very low viz,that a buddy can become a liability versus an asset,but this is not a common dive position for most. I am unsure what type of research diving they refer to,but I do a lot of research cave diving for two states,and a buddy is an essential tool.
We have redundant equipment,but not a redundant brain,so having a buddy for this and life support is prudent. There are many people who want to do solo diving because they don't have buddy,but are determined to do it because they came to dive. This is probably the least beneficial reason to solo dive,and history will show we have had accidents which resulted in near-fatalities and fatalities. It is smart to have a lot of cave diving experience before attempting this activity,and also do progressive penetration,because line doesn't guarantee an exit.