Review submit/cancel actions on comments

• - Avoid actions to be unaccessible/hidden by the '+' button:

"once you reach several lines of comments, the action to submit the comment is hidden by the “+” round button, which downgrades the user experience"
by Gregory Carlin

• Analyse also if the usability pattern 'press enter to submit' is a nice to have
  (is there a workaround for the mobile limitation?)

"During a discussion about consistency between ARender connector and the rest of Web UI this morning, it was mentioned that the most common command in other systems (ie/ Slack) for Submit vs New Line in comments is Submit => Enter; New Line => Shift + Enter. Are their any plans to modify Web UI comments behavior to follow the rest of the flock?"
by Karin Touchie