diff --git a/public/javascripts/speed_grader.js b/public/javascripts/speed_grader.js
index bee8181ed77..fde546710a5 100644
--- a/public/javascripts/speed_grader.js
+++ b/public/javascripts/speed_grader.js
@@ -114,6 +114,8 @@ let anonymizableStudentId
 let anonymizableAuthorId
 let isModerated
 
+let commentSubmissionInProgress
+
 let $window
 let $full_width_container
 let $left_side
@@ -2860,6 +2862,13 @@ EG = {
   },
 
   addSubmissionComment(draftComment) {
+    // Avoid submitting additional comments if a request is already in progress.
+    // This can happen if the user submits a comment and then switches students
+    // (which attempts to save a draft comment) before the request finishes.
+    if (commentSubmissionInProgress) {
+      return false
+    }
+
     // This is to continue existing behavior of creating finalized comments by default
     if (draftComment === undefined) {
       draftComment = false
@@ -2875,6 +2884,8 @@ EG = {
       // that means that they did not type a comment, attach a file or record any media. so dont do anything.
       return false
     }
+
+    commentSubmissionInProgress = true
     const url = `${assignmentUrl}/${isAnonymous ? 'anonymous_' : ''}submissions/${
       EG.currentStudent[anonymizableId]
     }`
@@ -2909,11 +2920,13 @@ EG = {
       window.setTimeout(() => {
         $rightside_inner.scrollTo($rightside_inner[0].scrollHeight, 500)
       })
+      commentSubmissionInProgress = false
     }
 
     const formError = (data, _xhr, _textStatus, _errorThrown) => {
       EG.handleGradingError(data)
       EG.revertFromFormSubmit({errorSubmitting: true})
+      commentSubmissionInProgress = false
     }
 
     if ($add_a_comment.find("input[type='file']:visible").length) {
@@ -3759,6 +3772,8 @@ export default {
       speedGraderJSONErrorFn
     )
 
+    commentSubmissionInProgress = false
+
     $.when(getGradingPeriods(), speedGraderJsonDfd).then(setupSpeedGrader)
 
     // run the stuff that just attaches event handlers and dom stuff, but does not need the jsonData
diff --git a/spec/javascripts/jsx/speed_graderSpec.js b/spec/javascripts/jsx/speed_graderSpec.js
index 7607b9bb715..d7aeb06ffb9 100644
--- a/spec/javascripts/jsx/speed_graderSpec.js
+++ b/spec/javascripts/jsx/speed_graderSpec.js
@@ -4630,6 +4630,48 @@ QUnit.module('SpeedGrader', rootHooks => {
 
           revertFromFormSubmit.restore()
         })
+
+        test('does not submit a comment request if one is already in progress', () => {
+          $.ajaxJSON.resetHistory()
+
+          SpeedGrader.EG.addSubmissionComment('hello')
+          SpeedGrader.EG.addSubmissionComment('hello???')
+          strictEqual($.ajaxJSON.callCount, 1)
+        })
+
+        test('submits a comment request if the preceding request succeeded', () => {
+          $.ajaxJSON.resetHistory()
+          $.ajaxJSON.callsFake((_url, _method, _form, success, _error) => {
+            sinon.stub(SpeedGrader.EG, 'revertFromFormSubmit')
+            sinon.stub(window, 'setTimeout')
+
+            success([])
+
+            window.setTimeout.restore()
+            SpeedGrader.EG.revertFromFormSubmit.restore()
+          })
+
+          SpeedGrader.EG.addSubmissionComment('ok')
+          SpeedGrader.EG.addSubmissionComment('ok!')
+          strictEqual($.ajaxJSON.callCount, 2)
+        })
+
+        test('submits a comment request if the preceding request failed', () => {
+          $.ajaxJSON.resetHistory()
+          $.ajaxJSON.callsFake((_url, _method, _form, _success, error) => {
+            sinon.stub(SpeedGrader.EG, 'revertFromFormSubmit')
+            sinon.stub(SpeedGrader.EG, 'handleGradingError')
+
+            error()
+
+            SpeedGrader.EG.handleGradingError.restore()
+            SpeedGrader.EG.revertFromFormSubmit.restore()
+          })
+
+          SpeedGrader.EG.addSubmissionComment('no')
+          SpeedGrader.EG.addSubmissionComment('noooooo')
+          strictEqual($.ajaxJSON.callCount, 2)
+        })
       })
 
       QUnit.module('#handleGradeSubmit', hooks => {