This is not a MacRumours or Xenforo only problem.
I ended up here after having a really frustrating time posting on
www.whirlpool.net.au (an internet focussed forum in Australia) where I was having significant issues with text randomly replacing itself.
This is a text only forum that runs custom code. This is pointing to it being a Safari issue. It is almost like there is a random undo happening but it isn't that either as the issue happens when text is typed, and it is not always the same.
Currently running Sonoma 14.3 (23D56) on a MacBook pro, using Safari Version 17.3 (19617.2.4.11.8)
Running ABP 2.2.13
This has only just started to be a problem in the last couple of days for me.
Apart from having random previously deleted text appearing back in posts I have also had text overwriting a line. It is feeling very much like a memory management issue within Safari which concerns me significantly.