On Github you can easily see what happens, comments are surrounded by a black border, the name of the comment author and the date are clearly visible and have a different background color from the comment text. Actions like closing and re-opening are distinctly different from comments and are color coded (green -> re-opened, red -> closed, purple -> merged). Emoticons are part of the comment box and don't visually drift into the next one.
Gitlab on the other hand separates comments by a thin (1px) light-grey line that is hardly visible on low contrast monitors like TN displays. Closing and re-opening is also displayed as a light-grey icon on a white background. The author's name has the same color as the comment text, with the date being, again, light-grey. Nothing keeps the contents of a comment together, it's all just text on a white background. The emoticons are just floating around the comments, with the same margin to the next comment as to the comment they are belonging to. So you have to know that emoticons are always below a comment.
Github's design is far, far superior to Gitlab's design because it allows skimming instead of concentrating on finding where each comment begins and ends.