Coming from a downstream bug report: https://gitlab.gnome.org/GNOME/evolution/-/issues/1339 The "insertHTML" command, when replacing a selection, can cut too many letters (one more than expected) and replace it with ` `. Steps to reproduce: a) run: MiniBrowser --editor-mode b) open the inspector and paste into the console this command: document.body.outerHTML="<body style=\"-webkit-line-break: after-white-space;\"><div>aaaaaaaa aa popular belief, aaaaa aaaaa aa aaa aaaaaa aaaaaa aaaa. aa aaa aaaaa aa a aaaaa aa aaaaaaaaa aaaaa aaaaaaaaaa aaaa aa</div><div class=\"-x-evo-signature-wrapper\"><span class=\"-x-evo-signature\" id=\"none\"></span></div></body>" c) then paste these two commands - the first selects the text, the second replaces it (when pasted separately the selection is discarded, which doesn't reproduce the bug): document.getSelection().setBaseAndExtent(document.body.firstElementChild.firstChild, 12, document.body.firstElementChild.firstChild, 26); document.execCommand("insertHTML", false, "<a href=\"https://\">popular belief</a>") The command basically selects the "popular belief" text and replaces it with a link. Use Undo to see what had been selected before the "insertHTML" command execution. Actual outcome: ... <a ...>popular belief</a> aaa... (instead of the coma, there's an ' ' Expected outcome: ... except of the there's left the comma Observations: 1) it doesn't matter whether it's a comma or a letter at the end of the selection; selecting one letter less will reproduce the problem too, but cutting the 'f' letter instead 2) the length of the <div> matters - using one letter less (cut the last `a`) will not reproduce the bug 3) not using "-webkit-line-break: after-white-space;" will not reproduce the bug 4) shifting the selection start more to the left will not reproduce the bug (like from 11 to 26, instead of 12 to 26)