I've got a simple, 16-year-old blog for which I do a regular Friday post. Not using any exotic SEO plugins, anything like that. All of a sudden, today — maybe sometime in the last week? — WP seems to be generating an automatic anchor for text which simply uses a hashtag character (Unicode U+0023, AKA "pound sign," AKA "number sign"). And yes, I've tried using the ampersand-num-semicolon HTML entity equivalent — no difference.
For instance, in the draft for my post today I've got this text string:
#57
…which, in the post preview's HTML, looks like this:
<a rel="tag" class="hashtag u-tag u-category" href="https://johnesimpson.com/blog/tag/57/">#57</a>
…and in a browser window, appears and functions like any other anchor/link.
Needless to say, there are no such "57" anchors anywhere in the blog. The last time I used a # character was in a mid-August post; in that post, no anchor tag appears around the numbers. So it's something which has changed in the last five weeks.
What the heck? Suggested workarounds?
(BTW, this is happening whether I use a Classic block, a regular paragraph block, etc.)
(BTW Number 2: This kind of sh!t drives me crazy about WP.)

FWIW: selecting the pound sign and designating it as “inline code” makes the anchor disappear… but does, of course, make the character display in a fixed font instead of the blog’s standard one.