In HTML, the less-than sign is used at the beginning of tags.
if you use this bracket "<test1>" in content, your bracket content will be unvisible, html renderer is assuming it as a html tag, changing chars with it's ASCI numbers prevents the issue.
with html friendly name:
<test1>
or with asci number:
<test1>
or comple asci:
<test1>
result: <test1>
asci referance: https://www.w3schools.com/charsets/ref_html_ascii.asp