GMail has a weirdish feature that probably very few people except me know about. When using it with a Hebrew user interface, invisible control characters—LRM, RLM, RLE, LRE and the like—are added to some strings to make them appear correctly in a mixed-direction interface.
Most notably, they are added to email addresses. I sometimes want to copy these email addresses as text, and my mouse pointer picks the control characters as well. Of course, these control characters are by themselves invisible to humans, but very much visible to computers, and an email address with these characters is not correct, even if it appears to be the same to human eyes.
It already became a habit for me to carefully delete and manually restore the first and the last characters of an email address to make sure that the control characters are removed.
It would be better if GMail just used the <bdi> element or CSS bidi isolation. They are fairly well supported in modern browsers and provide better experience.