@swart@mastodon.cloud my #IndieWeb site https://tantek.com/, which runs its own software, doesn’t have any explicit length limit, nor does https://fed.brid.gy/, the service I use to federate to ActivityPub followers such as Mastodon instances.
Both client & server as it were. I haven’t seen it cause any problems with other instances yet.
For more about how an #IndieWeb setup works, and why, you might be interested in:
* https://tantek.com/2023/005/t3/indieweb-simpler-approach