when I saw this sub

A comment containing solely a #, informally referenced as a hashbrown and is oft used in such a manner to tag something, oft referred to as a hashtag. Due to the nature of reddit's comment system, the comment will appear to have no text in it, and will bypass reddit's error message of 'we need something here'. This method of making a comment is likely an oversight, and might be fixed in the future, however it probably will not be due to the hilarity and comedic value it has.

Fun fact: Some people try to do the hashtags on reddit, however, the 'hashbrown' causes the text to go extremely large. Sometimes this is thought of as a joke and people who try to correct it get made fun of because people can never make mistakes/has no idea it appears wrong on

/r/ihavereddit Thread Parent Link - i.imgur.com